498 Questions
Why is the immune system considered vital for survival?
To protect against infectious pathogens and cancer development
What can happen when individuals have immune deficiencies?
Increased susceptibility to infections and certain cancers
Which of the following is an example of a disorder caused by immune responses?
Allergies
What type of diseases are discussed in the chapter related to immunologic reactivity?
Diseases caused by too little or too much immunologic reactivity, and diabetes
In which disease is an abnormal protein, sometimes derived from immunoglobulins, deposited in tissues?
Amyloidosis
What is the main characteristic that distinguishes innate immunity from adaptive immunity?
Speed of response
Which type of immunity is conventionally referred to as the immune response?
Acquired immunity
Which component of the immune system provides immediate defense against microbes and damaged cells?
Innate immunity
What type of antigens does autoimmunity typically target?
Self antigens
Which immunity category involves mechanisms that adapt to exposure to foreign substances?
Acquired immunity
What term describes the immediate protective host reactions induced by innate immunity?
Rapid innate response
Which immunity type is considered the first line of defense against infectious pathogens?
Innate immunity
Which term refers to the intrinsic mechanisms that react immediately to provide defense?
Innate immunity
Which cells are primarily responsible for phagocytosing invaders in the blood?
Monocytes
What is the main function of tissue-resident macrophages like Kupffer cells in the liver?
Destroy invading microbes
Which plasma proteins are involved in the innate immune response and can be found in the complement system?
Complement proteins
What is the role of dendritic cells in the immune system?
Activate T cells
Which type of cells produce antimicrobial molecules like defensins in the body?
Epithelial cells
What is the origin of some tissue-resident macrophages like microglia in the brain?
Yolk sac or fetal liver
Innate lymphoid cells contribute to innate immunity by primarily functioning as:
Secretory cells
Which type of barrier plays a vital role in preventing microbial entry into the body?
'Epithelial' barrier
What is the primary function of dendritic cells?
Recognizing antigens and presenting peptides to T lymphocytes
How do dendritic cells differ from macrophages?
Dendritic cells are not involved in destruction of offending agents
What is the role of cytokines secreted by dendritic cells?
Initiating inflammation
What distinguishes innate lymphoid cells (ILCs) from T lymphocytes?
Presence of T-cell antigen receptors
Which immune cells serve as sentinels that detect danger and initiate innate immune responses?
Dendritic cells
What is the main function of natural killer (NK) cells in immunity?
Destroying infected host cells
Which cell type plays a crucial role in innate immunity by activating other immune cells through the production of inflammatory cytokines?
Mast cells
Which plasma protein is involved in innate immunity and coats microbes to promote phagocytosis?
C-reactive protein
Which pathway of the complement system may be activated by antibody-antigen complexes during adaptive immune responses?
Classical pathway
Which cell type provides protection against intracellular bacteria and viruses, serving as a first line of defense in innate immunity?
Natural killer cells
What is the main function of lung surfactant in innate immunity?
Providing protection against inhaled microbes
Which group of T cells is responsible for producing inflammatory cytokines and is essential in the early phases of immune reactions?
Th1
Which circulating protein plays a role in innate immunity by promoting phagocytosis through coating microbes?
Tumor necrosis factor
Which cell type is capable of reacting to microbes and producing mediators of inflammation, playing a role in innate immunity?
Tissue-resident macrophages
Which mechanism is involved in complement activation through the alternative pathway during innate immune responses?
Microbe activation
What is the primary function of mannose-binding lectin in the innate immune response?
Coating microbes for phagocytosis
What structures are recognized by cellular receptors participating in innate immunity?
Pathogen-associated molecular patterns
Which family of receptors includes the Toll-like receptors (TLRs) that are essential for host defense against microbes?
Pattern recognition receptors
Where are the Toll-like receptors (TLRs) located within cells?
Plasma membrane and endosomal vesicles
What is the function of NOD-like receptors (NLRs) in the immune response?
Detect a variety of substances including those from damaged cells
Which protein is activated by the inflammasome to generate the biologically active form of interleukin-1 (IL-1)?
Caspase-1
What type of mutations in NLRs can result in periodic fever syndromes called autoinflammatory syndromes?
Gain-of-function mutations
Which transcription factors are activated by Toll-like receptors to stimulate cytokine synthesis and adhesion molecules expression?
NF-KB and IREs
What do pattern recognition receptors detect within cells?
Foreign substances
What is the main function of the inflammasome in the immune response?
Generate the biologically active form of interleukin-1 (IL-1)
Which molecules are recognized by NOD-like receptors (NLRs) as signs of danger or damage?
Products from necrotic or damaged cells
What is the main function of STING pathway activation?
Producing antiviral cytokines
Which receptor enables neutrophils to detect bacterial proteins?
G protein-coupled receptors
What is the role of antibody-dependent cellular cytotoxicity (ADCC) mediated by NK cells?
Recognizing and destroying abnormal cells coated with IgG
How do NK cell inhibitory receptors contribute to immune function?
Preventing NK cells from attacking normal cells
Which cytokine activates macrophages to destroy ingested microbes?
Interferon-y (IFN-y)
What triggers the vascular and cellular components of inflammation during innate immune reactions?
Cytokines and mediators
How do Natural Killer (NK) cells contribute to early defense against intracellular microbial infections?
By secreting interferon-gamma (IFN-g)
What is the primary function of IL-12 in the immune response?
Activating killing of target cells
What is the main mechanism by which NK cells engage abnormal or infected cells?
Using activating and inhibitory receptors
How do mannose receptors contribute to innate immunity?
Inducing phagocytosis of microbes
What is the enzyme that is converted from an inactive to an active form in the inflammasome pathway?
Caspase-I
Which protein complex recognizes products of dead cells and some microbes to induce the secretion of interleukin I?
NLRP3
In the inflammasome pathway, what role does the adapter play?
Acting as a bridge between the sensor protein and caspase-I
Which cellular receptor family participates in recognizing urate crystals, lipids, and cholesterol crystals in various inflammatory conditions?
NLRs
What is the main outcome of the inflammasome pathway activation in response to urate crystals during gout inflammation?
Induction of interleukin I secretion
Which type of inflammation is associated with obesity-related type 2 diabetes and atherosclerosis due to abnormal deposition of cholesterol crystals?
Obesity-associated inflammation
Which class of receptors are responsible for detecting fungal glycans and eliciting inflammatory reactions to fungi on macrophages and dendritic cells?
C-type lectin receptors (CLRs)
What happens when infected or stressed cells reduce class I MHC expression?
Inhibitory receptors are not engaged, and activating receptors are expressed.
How do NK cells respond to healthy cells expressing ligands for activating receptors?
They remain inactive due to the engagement of inhibitory receptors.
What is the primary function of inhibitory receptors in NK cells' interactions with healthy cells?
To ensure NK cells do not attack normal cells
How do NK cells contribute to defense against virus-infected cells?
By directly killing infected cells
What distinguishes innate immunity from adaptive immunity in terms of memory?
Adaptive immunity has memory, while innate immunity does not.
How many different receptors does innate immunity use to recognize molecular patterns?
100
What is the result of reduced class I MHC expression in infected or stressed cells?
Activation of NK cells
Which type of immunity lacks memory or fine antigen specificity?
Innate immunity
What stimulates the more powerful adaptive immune response following innate immunity's defense functions?
Danger signals produced by innate immunity
How do inhibitory receptors help in preventing NK cells from attacking normal cells?
They ensure that inhibitory signals override activating signals
What is the role of humoral immunity in the adaptive immune system?
Protects against extracellular microbes and their toxins
What is the key feature that differentiates effector cells from memory cells in adaptive immunity?
Effector cells perform the function of eliminating microbes
What term describes lymphocytes that have not encountered the specific antigen they are programmed to attack?
Naïve cells
How do B lymphocytes contribute to adaptive immunity?
Secrete antibodies
What is the main function of cellular immunity in the adaptive immune system?
Defense against intracellular microbes
What is the process called when lymphocytes differentiate into effector and memory cells upon antigen recognition?
Clonal selection
Which immune cells express highly diverse receptors to recognize a wide variety of foreign substances?
T lymphocytes
How do lymphocytes of adaptive immunity interact with one another in lymphoid organs?
Anatomically segregate until activated by antigens
What is the primary mediator of humoral immunity? (in terms of secreted products)
Antibodies
What enzyme mediates recombination of gene segments in developing lymphocytes to generate antigen receptor diversity?
RAG-1 and RAG-2
Where does DNA sequence variation occur during the assembly of gene segments in lymphocyte maturation?
At sites where the gene segments are joined
Which cells contain recombined antigen receptor genes that result from somatic recombination?
T and B cells
What is the outcome of inherited defects in RAG proteins regarding lymphocyte development?
Failure to generate mature lymphocytes
In which regions of the antigen receptors do diverse amino acid sequences occur due to recombination of gene segments?
Variable regions
Which cells contain recombined genes encoding TCR in T cells and Ig in B cells, leading to diverse antigen receptor generation?
T and B cells
What is the enzyme product that facilitates the recombination of gene segments in developing lymphocytes?
RAG-1 and RAG-2
How can polyclonal (nonneoplastic) lymphocyte proliferations be distinguished from monoclonal (neoplastic) lymphoid tumors?
By assessing the diversity of antigen receptor rearrangements within a population of lymphocytes.
What is the role of Helper T lymphocytes in the immune system?
Activating other immune cells to destroy microbes
What distinguishes polyclonal (nonneoplastic) lymphocyte proliferations from monoclonal (neoplastic) lymphoid tumors?
Unique DNA rearrangement in each T or B cell
How are assays that assess the clonality of antigen receptor gene rearrangements helpful in diagnosing lymphoid neoplasms?
By distinguishing monoclonal from polyclonal lymphocyte proliferations
What is the function of cytotoxic (killer) T lymphocytes (CTLs) in the immune system?
Killing infected cells
Which gene rearrangements can differentiate nonneoplastic from neoplastic lymphoid cells?
$TCR$ or $Ig$ gene rearrangements
In diagnosing lymphoid neoplasms, what is the significance of unique DNA rearrangements in each T or B cell and its progeny?
$TCR$ or $Ig$ gene rearrangements detection
How do T lymphocytes recognize specific antigens?
By binding to MHC molecules
What is the role of the CD3 and δ proteins in T cells?
Form the TCR complex
What is the significance of MHC restriction in the immune system?
It ensures T cells only recognize cell-associated antigens
How many polypeptide chains are noncovalently linked to each T cell receptor (TCR)?
Six
Which region of the αβ TCR is responsible for binding to specific antigens?
Variable region
What is the main function of regulatory lymphocytes?
To limit immune responses
Where do T lymphocytes develop from precursors?
Thymus
What is the composition of the TCR in approximately 95% of T cells?
$\alpha\beta$ polypeptide chain dimer
What ensures that T cells only see cell-associated antigens?
MHC restriction
Where do yδ T cells tend to aggregate?
Epithelial surfaces
Which subset of T cells express markers found on NK cells?
NK-T cells
What is the main function of CD8+ T cells?
Destroying host cells harboring microbes
Which molecules initiate signals necessary for T cell activation?
CD4 and CD8
What is the role of integrins in T-cell function?
Promoting attachment to APCs
Which proteins are found on the surface of all mature, naive B cells?
IgM and IgD antibodies
Which cells differentiate into plasma cells after stimulation by antigen?
β lymphocytes
What is the estimated secretion rate of antibody molecules by a single plasma cell?
≥1000 molecules per second
Which receptor complex is responsible for antigen recognition in B lymphocytes?
B-cell antigen receptor (BCR) complex
Which immune cells are called sentinels for protecting against microbes trying to enter through epithelia?
γδ T cells
What proteins are essential for signal transduction in response to antigen recognition in B cells?
Iga and Igß
Which molecule is used by Epstein-Barr virus (EBV) as a receptor to enter and infect B cells?
CR2
Which cells are the most important antigen-presenting cells for initiating T-cell responses against protein antigens?
Dendritic Cells (DCs)
Where are dendritic cells located to capture antigens effectively?
Under epithelia and in the interstitia of tissues
What feature of dendritic cells accounts for their key role in antigen presentation?
Expression of many receptors for capturing and responding to microbes
What are immature dendritic cells called within the epidermis?
Langerhans cells
What do interdigitating DCs resemble due to their numerous fine cytoplasmic processes?
Dendrites
Which cells play a significant role in presenting antigens to naive T cells in lymphoid organs?
Follicular dendritic cells
Which cell type is ideally located to present antigens to naive T cells in lymphoid organs?
Dendritic Cells
What is the specific cell type that traps antigens bound to antibodies or complement proteins in germinal centers?
Follicular dendritic cells
Which cell type plays a role in humoral immune responses by presenting antigens to B cells in the germinal center?
Follicular dendritic cells
In which type of immunity do macrophages function as key effector cells for eliminating intracellular microbes?
Cell-mediated immunity
Where do T cells primarily develop within the immune system?
Thymus
Which of the following is a secondary lymphoid organ where adaptive immune responses occur?
Spleen
What is the primary function of the spleen in immune responses?
Trapping and initiating adaptive immune responses to blood-borne antigens
Where are cutaneous lymphoid systems located?
Under the epithelia of the skin
What is the role of antigen-presenting cells in lymph nodes?
Initiating adaptive immune responses in lymph nodes
What makes lymph nodes the site where the majority of adaptive immune responses occur?
Concentration of foreign antigens from tissues and epithelia
What functions do dendritic cells perform in the immune response?
Present antigens to naive T cells in lymphoid organs
Where is mucosal lymphoid tissue located?
Under the gastrointestinal and respiratory tracts' epithelium
Where are the T lymphocytes concentrated in lymph nodes?
Paracortex
What are the primary regions where immune responses are initiated in secondary lymphoid organs?
Paracortex
Where do B cells primarily reside in the spleen?
Splenic white pulp
What is the main function of follicular dendritic cells (FDCs) in lymph nodes?
Presenting antigens to B lymphocytes
Where are effector lymphocytes required to migrate in response to infection?
Sites of infection and inflammation
Which region of the spleen contains T lymphocytes surrounding arterioles?
Periarteriolar lymphoid sheaths
What is the role of dendritic cells (DCs) in secondary lymphoid organs?
Presenting antigens to T lymphocytes
What is the main function of the paracortex region in lymph nodes?
T lymphocyte concentration
What component of secondary lymphoid organs contains germinal centers if there has been an antigen response?
Follicles
In which region of the spleen do B cells mainly reside?
Splenic white pulp
What is the main function of MHC molecules in adaptive immunity?
Displaying peptide fragments for T cell recognition
Why are MHC molecules important in the context of autoimmune diseases?
They are linked to antigen recognition by T cells
What term describes the characteristic of the HLA system having thousands of distinct gene alleles in humans?
Polymorphism
Where are Class I MHC molecules primarily expressed?
On all nucleated cells
What is the significance of MHC gene products being divided into two major classes?
It influences the type of immune cells interacting with antigens
How does the polymorphism of the HLA system impact organ transplantation?
It presents a barrier due to allele diversity
What is the primary reason for naming human MHC molecules as human leukocyte antigens (HLA)?
As they were initially detected on leukocytes
What forms the cleft where peptides bind in class I MHC molecules?
01 and ds domains
Which cells recognize peptides bound to class I MHC molecules?
CD8+ T cells
Where are cytoplasmic proteins degraded to produce peptides that bind to class I MHC molecules?
Endoplasmic reticulum (ER)
What is the role of 2-microglobulin in class I MHC molecules?
Linkage to heavy chains
Which genes encode the a chains of class I MHC molecules?
HLA-A, HLA-B, HLA-C
Which cells recognize peptides presented by class I MHC molecules?
CD8+ T cells
What kind of antigens do class I MHC molecules present?
Virus- and tumor-specific antigens
What is the function of the polymorphic amino acid residues in class I MCH molecules?
Base of peptide-binding groove
Which proteins mediate communications between leukocytes according to the text?
Cytokines
In innate immune responses, what do cytokines primarily function to induce?
Inflammation
Which cells are the major sources of cytokines like TNF and IL-1 in innate immune responses?
Macrophages
What is the primary function of most cytokines in terms of action on neighboring cells?
Paracrine actions
Which immune cells produce cytokines principally in adaptive immune responses?
T lymphocytes
What is the term used for the actions of cytokines on neighboring cells?
Paracrine
Which type of cells can also produce cytokines in addition to macrophages and DCs?
Epithelial cells
What effect do cytokines have on virus replication in innate immune responses?
Inhibit replication
Which group of molecules mediates communications between leukocytes?
Cytokines
What is the main role of molecularly defined cytokines according to the text?
Mediate cell-to-cell communication
What role do CD8+ T cells play in the immune system?
Killing of tumor cells and eliminating viruses
How are CD8+ T cells restricted in their recognition of antigens?
They can only recognize peptides presented with class I MHC molecules
What is the function of B-microglobulin in MHC class I molecules?
Acts as a coreceptor binding to CD8+ T cells
What is the significance of the crystal structure of class II MHC molecules?
It demonstrates the presence of peptide-binding clefts facing outward
Where are class II MHC molecules encoded?
In a region called HLA-DR
What differentiates class I MHC-restricted CD8+ T cells from other T cell subsets?
They are involved in killing virus-infected and tumor cells
What is the primary function of the CD8+ T cell receptor (TCR) in antigen recognition?
Recognizing the MHC-peptide complex on antigen-presenting cells
How do CD8+ T cells interact with MHC-peptide complexes?
By recognizing both the MHC and peptide portions of the complex
What is the significance of the HLA genes' polymorphism in the immune system?
Ensure individuals can display any microbial peptide for protection
Why are grafts exchanged between individuals with different MHC profiles often rejected by the immune system?
Because they are considered foreign
Which cells recognize antigens only in the context of self class II molecules?
CD4+ T cells
What role do class II MHC molecules play in the immune response?
Present antigens to CD4+ T cells
Why do siblings have a 1 in 4 chance of sharing the same MHC profile?
'Random' recognition mechanism
Which region plays a crucial role in segregating cytoplasmic and internalized antigens for the appropriate immune response?
MHC molecules
What is the primary function of CD4+ T cells in the immune system?
Regulate immune responses
How do class II MHC molecules differ from class I MHC molecules in terms of antigen presentation?
'Intracellular' vs. 'Extracellular' antigen presentation
'Helper cells' in the immune system primarily interact with which type of molecule on cell surfaces?
'Self' class II MHC molecules
What type of immune response is mainly triggered by class II MHC molecules presenting antigens?
Th2 cell-mediated response against extracellular microbes
What is the primary function of adjuvants given with a protein antigen during immunization?
To stimulate innate immune responses
Which cells are responsible for carrying microbial antigens to draining lymph nodes?
Dendritic cells
In the immune response to tumors and transplants, what may provide 'signal 2' for activating adaptive immunity?
Substances from necrotic cells
Which cytokines are mainly responsible for promoting lymphocyte proliferation and differentiation?
IL-2 and IL-4
Which molecules function cooperatively to activate antigen-specific lymphocytes during innate immune responses?
Costimulators and MHC molecules
Which type of cytokines primarily serve to limit and terminate immune responses?
IL-10 and TGF-ß
What is the main role of Br proteins (CD80 and CD86) in immune responses?
Provide costimulatory signals to T cells
Which cells produce colony-stimulating factors (CSFs) to stimulate blood cell colony formation?
Marrow stromal cells, T lymphocytes, and macrophages
Which receptors on innate immune cells recognize microbial antigens initially?
Pattern recognition receptors
What practical therapeutic applications have been derived from knowledge about cytokines?
Inhibiting cytokine production for controlling inflammation
During immune responses, what ensures that adaptive immunity is triggered by microbes and not harmless substances?
'Signal 2'
Patients with rheumatoid arthritis often respond well to which type of therapy mentioned in the text?
TNF antagonists
What is the first line of defense in immune responses that also activates adaptive immunity?
Pattern recognition receptors
Which cells primarily produce GM-CSF and IL-3 among others?
T lymphocytes
Which cells use membrane-bound antibody molecules to recognize various chemical types of antigens?
B lymphocytes
What is the function of IL-10 in immune responses?
To limit and terminate immune responses
'Signal 1' in immune responses refers to the recognition of antigens complexed with which molecules on the cell surface?
MHC molecules
Which cytokines stimulate hematopoiesis?
GM-CSF and IL-3
What is the result of inhibiting cytokine production or actions according to the text?
Control of harmful effects of inflammation
Which group of cytokines is associated with promoting lymphocyte proliferation among others?
Interleukins (ILs)
Which cells secrete the cytokine IFN-$ ext{γ}$, a potent macrophage activator?
Helper T cells
What stimulates B cells to differentiate into IgE-secreting plasma cells?
IL-4
During classical macrophage activation, which combination of factors results in the production of microbicidal substances?
CD40 and IFN-$ ext{γ}$
Which cells bind to IgE-coated microbes like helminthic parasites to eliminate them?
Eosinophils
Which cells induce the production of eosinophils in the marrow and activate eosinophils at immune response sites?
Th2 cells
What is the main function of Th1 subset cells?
Secrete IFN-$ ext{γ}$
Which molecules are engaged during the interaction where CD4+ helper T cells recognize antigens displayed by macrophages or B lymphocytes?
CD40L and CD40 receptor
Which type of cells differentiate into effector cells that secrete distinct sets of cytokines and perform different functions?
Effector T cells
What is the primary function of IL-5 secreted by Th2 cells?
Activate eosinophils at immune response sites
Which cytokine is secreted by Thl subset cells, leading to the activation of macrophages?
IFN-$ ext{γ}$
What is the main function of Th17 cells in the immune system?
Recruit neutrophils and monocytes to destroy extracellular bacteria and fungi
What is the primary role of activated CD8+ T lymphocytes?
Destroy infected cells harboring microbes in the cytoplasm
How do B lymphocytes respond upon activation?
Endocytose antigens and present peptides to helper T cells
What is the main function of plasma cells derived from B lymphocytes?
Produce different classes of antibodies to eliminate extracellular microbes
What is the role of CTLs in tumor immunity?
Kill tumor cells by recognizing tumor-specific antigens
What is the significance of antibody responses to protein antigens being T-dependent?
Require T cell help for optimal antibody production
What is the unique function of helper T cells in antibody responses?
Activate B cells by providing necessary signals and cytokines
What distinguishes innate immunity from adaptive immunity in terms of memory?
Adaptive immunity has memory cells after exposure to antigens.
How do NK cells primarily contribute to defense against virus-infected cells?
By directly killing infected cells.
Where are the T lymphocytes concentrated in lymph nodes?
Paracortex region
Which family of receptors includes Toll-like receptors (TLRs) essential for host defense against microbes?
Pattern recognition receptors
What is the primary function of IL-5 secreted by Th2 cells?
Promote eosinophil production
Where do B lymphocytes differentiate into IgE-secreting plasma cells?
Bone marrow
What is the main outcome of the inflammasome pathway activation in response to urate crystals during gout inflammation?
Release of inflammatory cytokines
DNA sequence variation occurs during the assembly of gene segments in which stage of lymphocyte maturation?
B cell development
What type of immune response is characterized by the production of antibodies mainly of the IgM class?
T-independent
Which process improves the quality of the humoral immune response by stimulating the production of antibodies with high affinities for antigens?
Affinity maturation
What is the main outcome of T-dependent responses that is absent in T-independent responses?
Ig isotype switching
Which cells secrete cytokines that work together to stimulate B cells in the immune response?
Helper T cells
Which molecule induces the production of antibodies with different classes (isotypes) through helper T-cell actions?
CD40L
What feature distinguishes T-dependent responses from T-independent responses in terms of antibody production?
Ig isotype switching
Which process leads to the initiation of B-cell activation by engaging many antigen molecules on each B cell?
Epitope recognition
What is the main characteristic that differentiates T-independent responses from T-dependent responses?
$IgM$ secretion
'Isotype switching' and 'affinity maturation' are features primarily observed in which type of immune response?
$\text{Adaptive}$
What is the primary function of T follicular helper (TrH) cells in the immune response?
Stimulate B lymphocytes in germinal centers
Which antibody type is secreted from mucosal epithelia to neutralize microbes in respiratory and gastrointestinal tracts?
IgA
Which antibodies activate the complement system by the classical pathway?
IgG
What is the role of IgE antibodies in combating parasites?
Activate eosinophils to kill parasites
Where do long-lived memory cells primarily reside in the body?
Bone marrow
Which cells are responsible for continuously producing antibodies in the bone marrow over extended periods?
Plasma cells from germinal centers
Why do long-lived memory cells respond faster and more effectively upon reexposure to antigens?
They carry diverse receptors for antigens
What is the main function of dendritic cells in the immune system?
Recognize antigens and present them to lymphocytes
What is the underlying cause suspected in many hypersensitivity diseases?
Normal regulation of immune responses
Which type of genes have been implicated in the development of hypersensitivity diseases?
Both HLA and non-HLA genes
What is the primary mechanism of tissue injury in hypersensitivity reactions?
Effector mechanisms of defense against pathogens
Which cells are involved in causing tissue injury in hypersensitivity reactions?
Th2 cells, IgE antibodies, mast cells
How can hypersensitivity reactions be classified?
By the underlying immunologic mechanism
What is the cause of issues in hypersensitivity reactions?
Poorly controlled reactions
Which group of diseases is associated with immune responses against environmental antigens?
Allergy
What are the functions of CD4+T cells primarily mediated by?
Cytokines
Which immune cells are responsible for killing virus-infected and tumor cells?
NK cells
What do antibodies secreted by plasma cells primarily do?
Neutralize microbes
In immunology, what term is used to describe the transfer of immunity to neonates through antibodies?
Passive immunity
What is the term used to describe immune reactions that cause tissue injury?
Hypersensitivity reactions
Which group of disorders is characterized by the failure of tolerance to self-antigens?
Autoimmune disorders
Which type of diseases are caused by a defective immune system?
Immunodeficiency diseases
What is the primary cause of tissue injury in cell-mediated immune disorders?
T lymphocytes
Which type of hypersensitivity involves the binding of antigen to IgE on mast cells?
Type I hypersensitivity
In immune complex-mediated disorders, where do antigen-antibody complexes deposit and induce inflammation?
In tissues
What is the term for the leukocytes recruited in immune complex-mediated disorders that produce tissue damage through enzyme release and free radicals?
Neutrophils
Which cells are responsible for causing tissue injury in immediate (Type I) hypersensitivity reactions?
Mast cells
What is the primary outcome of antibody-mediated disorders (type II hypersensitivity)?
Tissue inflammation
Which antibody type plays a role in injurious reactions by promoting phagocytosis or lysis of cells?
IgG
What is the antigen-antibody interaction primarily responsible for in immune complex-mediated disorders?
Tissue inflammation
Which type of hypersensitivity is characterized by the deposition of antigen-antibody complexes in tissues?
Type III hypersensitivity
What is the main impact of immediate (Type I) hypersensitivity reactions on a sensitized individual?
Systemic reaction
What is the primary role of IL-13 in type I hypersensitivity reactions?
Enhances IgE production and stimulates mucus secretion
In type I hypersensitivity reactions, what is unique about the late-phase reaction compared to the immediate reaction?
It is characterized by tissue infiltration with various leukocytes
What is the main function of Th2 cells in immediate hypersensitivity disorders?
Promoting inflammation
Which cytokine is crucial for B cell class switching to IgE in type I hypersensitivity reactions?
Interleukin-4 (IL-4)
What is the immediate reaction in type I hypersensitivity characterized by?
Vasodilation and vascular leakage
Which cell type is a key effector in type I hypersensitivity reactions due to its involvement in tissue destruction?
Eosinophil
Which of the following cytokines is NOT produced by Th2 cells as part of the type I hypersensitivity response?
Interleukin-6 (IL-6)
What is the primary mechanism through which Th2 cells attract more Th2 cells and other leukocytes to the site of a hypersensitivity reaction?
Secretion of chemokines
What is a characteristic feature of the late-phase reaction following immediate hypersensitivity disorders?
Tissue infiltration with eosinophils and neutrophils
How do Th2 cells contribute to the development of allergic reactions?
By stimulating inflammation and IgE production
Which cytokine is NOT typically produced by Th2 cells in type I hypersensitivity reactions?
Interferon-gamma (IFN-gamma)
What is the primary function of mast cells in immediate hypersensitivity reactions?
Release of biologically active mediators
Where are mast cells commonly found in tissues, contributing to local immediate hypersensitivity reactions?
Near small blood vessels and nerves
What do mast cells contain in their cytoplasmic granules that contribute to immediate hypersensitivity reactions?
Acidic proteoglycans
Which group is predictably most responsive to antagonists of Th2 cytokines like IL-4 and IL-5?
Th2-high individuals
What type of responses do type 2 Ilcs in tissue initially provide before the development of Th2 responses?
Cytokine response to epithelia
What triggers the activation of mast cells and basophils by binding to receptors on the cell membrane?
C5a and C3a
What is the primary difference between mast cells and basophils?
Presence in tissues
What term describes the process where multivalent antigens cross-link adjacent IgE antibodies on mast cells?
Antigen cross-linking
Which of the following is NOT a mast cell secretagogue triggering their activation?
Thrombin
What is the role of FceRI in mast cells and basophils?
Specific for the Fc portion of IgE
Which physical stimuli can trigger the activation of mast cells?
Heat and cold
What do mast cells release upon activation that is responsible for immediate hypersensitivity reactions?
Histamine
What characteristic separates basophils from mast cells in terms of location?
Presence in tissues
What do multivalent antigens do when they bind to adjacent IgE antibodies on mast cells?
Cross-link antibodies
What type of molecules bind to receptors on mast cells to trigger their activation?
Complement components C5a and C3a
Which mediator is NOT derived from arachidonic acid in mast cells?
Histamine
What is the most abundant mediator produced in mast cells by the cyclooxygenase pathway?
Prostaglandin D
Which cytokine amplifies the Th2 response in immediate hypersensitivity reactions?
IL-4
What is the role of Platelet-activating factor (PAF) in immediate hypersensitivity reactions?
Leukocyte recruitment
Which cell population is often abundant in the late-phase reaction of immediate hypersensitivity disorders?
Eosinophils
What is a unique protein released by activated eosinophils that can damage tissues?
Major basic protein
Which crystal found in eosinophils promotes inflammation and enhances Th2 responses?
Charcot-Leyden crystals
'Late-phase reaction' in immediate hypersensitivity involves the recruitment of leukocytes that:
(a) Amplify and sustain the inflammatory response without additional exposure to antigens.
What is the main function of cytokines like IL-1 and TNF produced by mast cells?
Promote leukocyte recruitment.
What is the primary function of histamine released by mast cells?
Increasing vascular permeability
Which enzyme found in mast cell granules contributes to tissue damage and generation of kinins?
Chymotrypsin
Which class of mediators serves to package and store amines within mast cell granules?
Proteoglycans
What is the parent compound that is converted to leukotrienes and prostaglandins during mast cell activation?
Arachidonic acid
Which enzyme is responsible for converting membrane phospholipids to arachidonic acid during mast cell activation?
Phospholipase A2
Which of the following is a function of neutral proteases like chymase found in mast cell granules?
Lead to tissue damage
What is the role of heparin in mast cell granules?
Serve as an anticoagulant
Which enzyme is activated during mast cell activation leading to the production of leukotrienes?
5-lipoxygenase
What category do arachidonic acid-derived products belong to in mast cell granules?
Lipid mediators
What is a major function of lipid mediators produced from arachidonic acid during mast cell activation?
Acting as pro-inflammatory agents
What genetic factor determines susceptibility to immediate hypersensitivity reactions?
Atopy
Which cytokines have genetic polymorphisms that may contribute to allergic reactions?
IL-3, IL-4, IL-5
What is the role of broad-spectrum anti-inflammatory drugs in managing allergies?
Long-term suppression of allergic reactions
What percentage of atopic individuals have a positive family history of allergies?
50%
Which chromosome region shows linkage to polymorphisms affecting reactivity to certain allergens?
Chromosome 6
What environmental factor is highlighted as an important predisposing factor for allergies?
Urban lifestyle
In patients with asthma, what genes show linkage to polymorphisms affecting allergic reactions?
Genes for cytokines like IL-3 and GM-CSF
'Atopic' individuals tend to have higher levels of which substance compared to the general population?
'Helper' T cells
Which genetic factor is suggested to permit reactivity to certain allergens?
HLA alleles
'Immediate hypersensitivity reactions are genetically determined' refers primarily to what characteristic?
'Susceptibility'
What is the term used to describe the phenomenon where early childhood exposure to microbial antigens potentially prevents subsequent pathologic responses against common environmental allergens?
The hygiene hypothesis
Which statement best describes the primary observation made about dogs, cats, and chimpanzees in relation to allergies in the provided text?
Environment plays a significant role in allergic disease development.
What triggers bronchial asthma, an allergic lung disease, according to the text?
Nonimmune stimuli such as temperature variations
Why have commercial airlines largely stopped serving peanuts or foods containing peanuts according to the text?
Due to the risk of severe allergic reactions to minute quantities of peanuts.
What type of reactions affect about 10% to 20% of the population and involve localized responses to common environmental allergens?
Immediate hypersensitivity reactions
In systemic anaphylaxis, what is characterized by vascular shock, widespread edema, and respiratory distress?
Laryngeal edema
What can trigger anaphylaxis in sensitized individuals following exposure in the community setting?
Insect toxins like bee venom
What is the primary risk associated with severe allergic reactions within minutes after exposure to allergens according to the text?
'Anaphylactic shock'
'Local Immediate Hypersensitivity Reactions' involve localized responses to which of the following?
'Immediate reaction' environmental allergens
'Systemic Anaphylaxis' may occur after administration of foreign proteins or exposure to food allergens, but primarily involves what type of response?
'Immediate Type I hypersensitivity'
What is the primary responsibility of mediators in Type I hypersensitivity reactions?
Causing immediate vascular and smooth muscle reactions
Which antibodies are recognized by phagocyte Fc receptors during phagocytosis in Type II hypersensitivity reactions?
IgG antibodies
In Type II hypersensitivity reactions, which antibodies may be specific for exogenous antigens?
IgG antibodies
What is the main cause of tissue injury in Type II hypersensitivity reactions?
Deposition of antibodies on cell surfaces
Which phase of the reaction is responsible for the manifestation of inflammation in Type I hypersensitivity reactions?
Late-phase reaction
What is the consequence of IgG antibodies being recognized by phagocyte Fc receptors?
Depletion of antibody-coated cells
Which type of antibodies are involved in opsonization and phagocytosis in Type II hypersensitivity reactions?
IgG antibodies
Which cells are primarily responsible for cell lysis in antibody-dependent cell-mediated cytotoxicity (ADCC)?
NK cells
In which of the following situations does cell lysis proceed without phagocytosis?
Transfusion reactions
What is the main contribution of antibody-dependent cell-mediated cytotoxicity (ADCC) to common hypersensitivity diseases according to the text?
Cell lysis
In autoimmune hemolytic anemia, agranulocytosis, and thrombocytopenia, what do individuals produce antibodies against?
Their own blood cells
What characterizes hemolytic disease of the fetus and newborn (erythroblastosis fetalis) regarding antigenic differences?
Antigenic difference between mother and fetus
What causes destruction of fetal red cells in hemolytic disease of the fetus and newborn?
IgG antibodies
Certain drug reactions may generate new antigenic epitopes against which individuals react. What specifically causes the generation of these new epitopes?
Conformational changes to antigens
In which type of reaction does the drug bind to plasma membrane proteins on host cells leading to antibody production against the drug-protein complex?
Type II hypersensitivity
What is the main mechanism responsible for tissue injury in some forms of glomerulonephritis and vascular rejection in organ grafts?
Antibody-mediated inflammation
In which disorder do antibodies reactive with acetylcholine receptors in the motor end plates of skeletal muscles block neuromuscular transmission?
Myasthenia gravis
Which substances released by leukocytes during activation can damage tissues by digesting basement membrane, collagen, elastin, and cartilage?
Lysosomal enzymes and proteases
What is the primary basis of Graves disease?
Antibody-mediated stimulation of cell function
Which type of hypersensitivity mainly produces tissue damage by eliciting inflammation at the sites of antigen-antibody complex deposition?
Type III hypersensitivity
In which type of reaction are antibodies directed against cell surface receptors, impairing or dysregulating function without causing cell injury or inflammation?
Cellular dysfunction
Which leukocytes are activated by engagement of their C3b and Fc receptors during inflammation?
Granulocytes and monocytes
What is the role of anaphylatoxins C3a and C5a in antibody-mediated inflammation?
Vascular permeability increase
Which cellular process results from activation of leukocytes' C3b and Fc receptors during inflammation?
Chemotaxis of granulocytes and monocytes
What enzyme product contributes to the digestion of basement membrane, collagen, elastin, and cartilage by leukocytes during inflammation?
Collagenase
What is a defining characteristic of immune complex-mediated diseases?
Systemic nature with a tendency to involve the kidney, joints, and small blood vessels
What is one of the common sites for preferential immune complex deposition in immune complex-mediated diseases?
Joints
Serum sickness is a prototype of which type of immune complex disease?
Systemic immune complex disease
Which phase of the pathogenesis of systemic immune complex disease involves the formation of immune complexes?
Phase 1
What is the primary reason serum sickness is now infrequent in modern times?
Decreased use of immunized horse serum
Why is serum sickness used as an informative model for systemic immune complex disorders?
As it provides insights into various phases of pathogenesis
Which organ is often preferentially involved in systemic immune complex diseases such as glomerulonephritis?
Kidney
What is a common characteristic of immune complexes that tend to lead to tissue deposition and disease?
Medium size and formed under conditions of slight antigen excess
In which organs does immune complex disease often affect due to the concentration and deposition of immune complexes?
Glomeruli and joints
What happens approximately one week after the introduction of a protein antigen?
Secretion of antibodies into the blood
Which phase involves the formation of circulating antigen-antibody complexes that are later deposited in vessels?
Deposition phase
Which factor plays a major role in determining whether immune complex formation leads to tissue deposition and disease?
Local vascular alterations
Where do immune complexes tend to become concentrated due to high pressure filtration of blood, leading to their deposition?
Kidneys and joints
What influences the pathogenicity of immune complexes in terms of size and conditions of formation?
Formation under slight antigen excess conditions
What is the primary cause of tissue injury in the Arthus reaction?
Fibrinoid necrosis caused by immune complex precipitation
What is the main difference between acute and chronic serum sickness?
Number of exposures to antigen
Which type of hypersensitivity involves chronic and destructive inflammation mainly mediated by T cells?
Type IV
What is the primary mechanism through which antibodies and immune complexes cause tissue injury?
Activation of leukocytes' Fc receptors
How does the Arthus reaction differ from delayed-type hypersensitivity (DTH) in terms of tissue injury?
Dominance of neutrophils in tissue destruction
Which type of hypersensitivity involves antibodies binding to cell surface receptors, causing functional derangements without cell injury?
Type II
What differentiates the immune complex deposition in membranous glomerulonephritis from that in vasculitides?
Morphologic changes in tissues
What is the primary role of antibodies in targeting opsonized cells for phagocytosis?
Coating cells with IgG and complement proteins
What is the main outcome of antigen diffusing into the vascular wall during the Arthus reaction?
Formation of large immune complexes
What happens when CD4+ T cells recognize antigens displayed by dendritic cells (DCs)?
Differentiation into Thi or Th17 cells driven by APC-produced cytokines
What is the main morphologic manifestation of immune complex injury discussed in the text?
Fibrinoid necrosis
Which clinical feature is NOT commonly associated with the acute inflammatory reaction initiated by immune complexes in tissues?
Cough
What is the significance of detecting complement proteins at the site of tissue injury during immune complex-mediated inflammation?
It supports the role of complement in pathogenesis
Which observation supports the idea that serum C3 levels can be used to monitor disease activity in certain cases?
Consumption of complement leading to decreased serum C3 levels
What is the main appearance of granular lumpy deposits of immunoglobulin and complement in the kidney when viewed under immuno-fluorescence microscopy?
Electron-dense deposits
Which cell type is primarily responsible for intense neutrophilic infiltration in fibrinoid necrosis associated with immune complex injury?
Neutrophils
What does the term 'acute vasculitis' refer to in the context of immune complex injury?
Inflammation of blood vessels
What is the main role of IFN-y-activated macrophages in the context of a delayed-type hypersensitivity reaction?
Express more class II MHC molecules for antigen presentation
What is the primary function of Th1 cells upon repeat exposure to an antigen?
Produce IFN-y to promote delayed-type hypersensitivity
How do IFN-y-activated macrophages contribute to eliminating offending antigens?
Enhance phagocytosis and antigen presentation
Which cytokines are secreted by IFN-y-activated macrophages to promote inflammation?
TNF and IL-1
What is the consequence of sustained activation of macrophages during a delayed-type hypersensitivity reaction?
Continued inflammation and tissue damage
Which cell type is responsible for the secretion of IL-17 and IL-22 in an inflammatory reaction?
Th17 cells
What is the main role of chemokines secreted by activated Th17 cells?
Recruiting neutrophils and monocytes
In a delayed-type hypersensitivity (DTH) reaction, what type of cells mainly accumulate around venules?
CD4+ T cells and macrophages
What is the morphological feature that characterizes delayed-type hypersensitivity (DTH) reactions?
Perivascular cuffing
With persistent antigens like tubercle bacilli, what type of cells dominate the infiltrate over a few weeks?
Macrophages
In fully developed lesions of delayed-type hypersensitivity reactions, what morphologic transformation do macrophages often undergo?
Epithelioid cell transformation
Which cytokines secreted by activated Th17 cells play a role in recruiting neutrophils to inflammation sites?
IL-17 and IL-22
What grossly visible small nodules are formed when aggregates of epithelioid cells are surrounded by lymphocytes?
Granulomas
What is the main characteristic that distinguishes a tuberculin reaction in a sensitized individual within 8 to 12 hours?
Reddening and induration of the site appear.
Which type of hypersensitivity reaction can be clinically observed as a tuberculin reaction?
Delayed-type hypersensitivity (DTH)
What is the main difference between granulomatous inflammation associated with helminthic infections and that induced by indigestible foreign bodies?
The presence of eosinophils in the former and Th1-cell activation in the latter.
What is the characteristic feature of contact dermatitis resulting from delayed hypersensitivity reactions?
Itchy, vesicular (blistering) dermatitis.
What is the primary mechanism through which tissue injury occurs in rheumatoid arthritis and multiple sclerosis?
CD8+ T cell-mediated inflammation.
What is the role of CD8+ CTLs in T cell-mediated reactions?
Killing antigen-expressing target cells.
What is the consequence of CTLs directed against cell surface histocompatibility antigens during graft rejection?
Contributing to graft rejection.
Which type of immune response involves CD8+ CTLs killing antigen-expressing target cells?
Type IV hypersensitivity
Virally infected cells present viral peptides through which type of molecules to be recognized by CD8+ T lymphocytes?
Class I MHC molecules
Tumor antigens are presented on the surface of tumor cells, primarily for which purpose?
Initiating host response to transformed cells
CD8+ T lymphocytes have a crucial role in which of the following processes?
Killing antigen-expressing target cells
Granulomatous reactions rich in eosinophils are typically associated with which type of immune responses?
Th2 responses
What is the primary significance of the presence of autoantibodies in the serum of some individuals?
May have a physiologic role
How is pathologic autoimmunity typically defined?
Absence of a well-defined cause of the disease
In which type of disorder are chronic inflammation and immune response sometimes directed against normally harmless microbes?
Immune-mediated inflammatory disease
Which autoimmune disease involves autoreactive T cells and antibodies specific for ß cells of the pancreatic islets?
Type 1 diabetes
What distinguishes organ-specific autoimmune diseases from systemic autoimmune diseases?
The number of involved tissues
Which autoimmune disease is characterized by antibodies directed against DNA, platelets, and protein-phospholipid complexes?
SLE
What is the underlying cause of autoimmunity?
Loss of self-tolerance
Which disease sits in the middle of the spectrum between organ-specific and systemic autoimmune diseases?
'Goodpasture syndrome'
'Immune-mediated inflammatory diseases' can be classified as autoimmune if the immune response is directed against what?
'Self antigens'
What is the primary function of perforin in the I cell-mediated killing of targets?
Facilitates the release of granzymes from the complex
Which molecule, expressed by activated CTLs, is homologous to TNF and triggers apoptosis in target cells by binding to the Fas receptor?
Fas ligand
What triggers the classical T cell-mediated inflammatory reaction known as DTH?
Secretion of cytokines
Which type of cells produce cytokines, notably IFN-γ, following exposure to certain agents and viral infections?
CD8+ T cells
Which molecule primarily activates macrophages to produce substances causing tissue damage and promoting fibrosis in CD4+ T cell-mediated hypersensitivity reactions?
IFN-γ
In I cell-mediated killing, what is the main function of granzymes released into the target cell cytoplasm?
Facilitate apoptosis by activating caspases
Which type of hypersensitivity reaction involves activated CD4+ T cells differentiating into Th1 and Th17 effector cells?
Type IV
What is the main role of activated CTLs in I cell-mediated killing?
Trigger apoptosis in target cells
Which subset of CD4+ T cells secrete IFN-γ to activate macrophages in hypersensitivity reactions?
Th1
What is a characteristic feature of DTH mediated by Th17 effector cells?
Recruitment of eosinophils to immune response sites
What is the primary function of central tolerance?
To eliminate immature self-reactive T and B cells
What happens to immature T cells that express TCRs specific for self antigens in the thymus?
They are killed by apoptosis
What is the purpose of self-tolerance in the immune system?
To prevent autoimmune diseases
What is the result of random somatic antigen receptor gene rearrangements in developing lymphocytes?
The generation of diverse antigen receptors
What is the difference between central tolerance and peripheral tolerance?
Central tolerance occurs during lymphocyte maturation, while peripheral tolerance occurs in peripheral tissues
What is the consequence of a failure in central tolerance?
The development of autoimmune diseases
What is the estimated proportion of B cells in the body that may have undergone receptor editing during their maturation?
One-fourth to one-half
What happens to self-reactive lymphocytes that escape central tolerance?
They are removed by peripheral tolerance mechanisms
What is the outcome if receptor editing does not occur?
Self-reactive lymphocytes undergo apoptosis
What is the purpose of central tolerance?
To remove self-reactive lymphocytes from the mature pool
What is the result of imperfect central tolerance?
Some self-reactive lymphocytes escape into the periphery
What is the primary function of AIRE in the thymus?
To stimulate the expression of some peripheral tissue-restricted self antigens in the thymus
What happens to developing B cells that strongly recognize self antigens in the bone marrow?
They reactivate the machinery of antigen receptor gene rearrangement and begin to express new antigen receptors
What is the outcome of rare patients with germline loss-of-function mutations in the AIRE gene?
Develop autoimmune polyendocrine syndrome
What determines the choice between deletion and development of regulatory T cells in the thymus?
The affinity of the antigen receptor on immature T cells for antigens present in the thymus
What is the role of thymic antigen-presenting cells in relation to self antigens?
To process and present self antigens in association with self MHC molecules to potentially self-reactive T cells
What is the fate of immature T cells that recognize self antigens in the thymus?
They are deleted through apoptosis
What is the primary mechanism by which regulatory T cells suppress immune responses?
Secretion of immunosuppressive cytokines such as IL-10 and TGF-B
What is the result of a mutation in the gene encoding IL-2 or the IL-2 receptor alpha or beta chain?
A rare multiorgan autoimmune disease
What is the phenotype of T cells that recognize self antigens but are rendered functionally unresponsive?
Anergy
What is the association between polymorphisms in the promoter of the CD25 gene and autoimmune diseases?
Regulatory T-cell defect
What is the name of the autoimmune disease caused by mutation of the gene encoding FOXP3?
IPEX
What is the function of regulatory T cells in the immune system?
To suppress immune responses to self antigens
What is the mechanism by which T cells that recognize self antigens are eliminated or inactivated?
Negative selection
What is the consequence of a defect in regulatory T cells?
Autoimmune disease
What is the primary function of regulatory T cells in placental mammals?
To prevent immune reactions against fetal antigens inherited from the father
What is the consequence of inherited mutations in CTLA4?
Systemic inflammatory diseases
What is the mechanism by which some tumors evade immune attack?
By using the same pathways of immune regulation as CTLA-4 and PD-1
What is the role of FOXP3 transcription factor in placental mammals?
To stably express regulatory T cells
Which molecule binds to the ligands PD-L1 and PD-L2?
PD-1
What is the outcome when mature B cells encounter self-antigen in peripheral tissues?
They become unable to respond to subsequent antigenic stimulation and may be excluded from lymphoid follicles
What type of signal is required for T cell activation in addition to antigen recognition?
Costimulatory signal
What is the therapeutic application of blocking CTLA-4 and PD-1?
Cancer treatment
What is the result of antigen presentation without adequate costimulation?
T cell anergy
What is the role of regulatory T cells in preventing immune responses?
Against self-antigens and commensal microbes
What is the function of CTLA-4 and PD-1?
Coinhibition
Why do resting DCs in normal tissues lead to anergy?
They do not express costimulatory molecules
What is the outcome when B cells encounter self-antigen in peripheral tissues in the absence of specific helper T cells?
They become anergic
What is the role of CD28 in T cell activation?
Costimulatory signal
Which molecule is structurally homologous to CD28 but serves the opposite function?
CTLA-4
What is the result of T cell recognition of self antigens in the absence of costimulation?
T cell anergy
What is the consequence of depleting FOXP3+ regulatory T cells in mice?
Fetal loss
How do T cells that recognize self-antigens die by apoptosis?
By expressing Bim without Bcl-2 and Bcl-x
What is the role of Fas ligand in deletion of mature T cells in the periphery?
Inducing apoptosis by the death receptor pathway
What is the consequence of T cells recognizing self-antigens in the periphery?
Induction of apoptosis
What is the mechanism by which Bim triggers apoptosis?
Mitochondrial pathway
What is the role of Bcl-2 and Bcl-x in T cells that recognize self-antigens?
Preventing apoptosis
What is the function of Fas in T cells that recognize self-antigens?
Inducing apoptosis
What is the significance of deletion of mature T cells in the periphery?
Prevention of autoimmune responses
What happens to self-reactive T cells if they engage with self-antigens?
They undergo Fas-mediated apoptosis
What is the main role of regulatory T cells?
To prevent immune reactions against self-antigens
What is the function of FasL on T cells?
To eliminate self-reactive B cells
What is the consequence of mutations in Fas or FasL?
Autoimmune lymphoproliferative syndrome (ALPS)
Which transcription factor is required for the development of regulatory T cells?
FOXP3
What is the characteristic of CD4+ regulatory T cells?
High levels of CD25 and FOXP3 expression
What is the main function of CD25 in regulatory T cells?
To bind IL-2 for survival and proliferation
What is the consequence of mutations in FOXP3?
Autoimmune diseases
What is the primary mechanism of immune tolerance in the thymus?
Clonal deletion of self-reactive T cells
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