Podcast
Questions and Answers
What are epitopes?
What are epitopes?
Which type of antigen is considered incomplete?
Which type of antigen is considered incomplete?
What is an example of a lipid antigen?
What is an example of a lipid antigen?
Which of the following is NOT a complete antigen?
Which of the following is NOT a complete antigen?
Signup and view all the answers
What element increases the immunogenicity of influenza virions?
What element increases the immunogenicity of influenza virions?
Signup and view all the answers
What is the primary function of the antigen-binding sites on an antibody?
What is the primary function of the antigen-binding sites on an antibody?
Signup and view all the answers
Which statement accurately describes a given B cell's ability to recognize epitopes?
Which statement accurately describes a given B cell's ability to recognize epitopes?
Signup and view all the answers
Which antibody isotype is most likely to predominate in mucosal areas?
Which antibody isotype is most likely to predominate in mucosal areas?
Signup and view all the answers
What differentiates the five antibody isotypes?
What differentiates the five antibody isotypes?
Signup and view all the answers
How does isotype switching occur in B cells?
How does isotype switching occur in B cells?
Signup and view all the answers
What role do MHCs play in tissue transplants?
What role do MHCs play in tissue transplants?
Signup and view all the answers
What is the process called that lymphocytes use to differentiate self from foreign MHCs?
What is the process called that lymphocytes use to differentiate self from foreign MHCs?
Signup and view all the answers
What must happen for T cells to become activated?
What must happen for T cells to become activated?
Signup and view all the answers
How do T cytotoxic cells recognize antigens?
How do T cytotoxic cells recognize antigens?
Signup and view all the answers
Which T cell type interacts with antigens presented by MHC II molecules?
Which T cell type interacts with antigens presented by MHC II molecules?
Signup and view all the answers
What happens if MHCs are not closely matched in a transplant?
What happens if MHCs are not closely matched in a transplant?
Signup and view all the answers
What is the role of antigen-presenting cells (APCs) in the immune response?
What is the role of antigen-presenting cells (APCs) in the immune response?
Signup and view all the answers
What must APCs do after bearing MHC-antigen complexes?
What must APCs do after bearing MHC-antigen complexes?
Signup and view all the answers
What are the two main branches of adaptive immunity?
What are the two main branches of adaptive immunity?
Signup and view all the answers
Which of the following correctly describes a T helper cell?
Which of the following correctly describes a T helper cell?
Signup and view all the answers
What is the primary difference between T and B cells?
What is the primary difference between T and B cells?
Signup and view all the answers
What is immunogenicity?
What is immunogenicity?
Signup and view all the answers
How do T and B cell receptors contribute to antigen recognition?
How do T and B cell receptors contribute to antigen recognition?
Signup and view all the answers
What is self-tolerance in the immune system?
What is self-tolerance in the immune system?
Signup and view all the answers
What is the role of haptens in immunology?
What is the role of haptens in immunology?
Signup and view all the answers
Which of the following describes a characteristic of innate immunity?
Which of the following describes a characteristic of innate immunity?
Signup and view all the answers
What is the primary source of antibodies in artificially acquired passive immunity?
What is the primary source of antibodies in artificially acquired passive immunity?
Signup and view all the answers
What does antiserum specifically target?
What does antiserum specifically target?
Signup and view all the answers
Which statement is true about the protection provided by artificially acquired passive immunity?
Which statement is true about the protection provided by artificially acquired passive immunity?
Signup and view all the answers
Which type of immune response is activated when an invader is detected by third-line defenses?
Which type of immune response is activated when an invader is detected by third-line defenses?
Signup and view all the answers
What are cytokines primarily responsible for in the immune response?
What are cytokines primarily responsible for in the immune response?
Signup and view all the answers
Which defenses are involved in the first line of immune defense?
Which defenses are involved in the first line of immune defense?
Signup and view all the answers
What happens after an invader overcomes first- and second-line defenses?
What happens after an invader overcomes first- and second-line defenses?
Signup and view all the answers
Which of the following describes what second-line defenses include?
Which of the following describes what second-line defenses include?
Signup and view all the answers
What effect do cytokines have on fever during the immune response?
What effect do cytokines have on fever during the immune response?
Signup and view all the answers
What type of defenses are categorized under 'Innate immunity'?
What type of defenses are categorized under 'Innate immunity'?
Signup and view all the answers
What initial symptoms did Hassan exhibit that led to his parents' assumption of overexertion?
What initial symptoms did Hassan exhibit that led to his parents' assumption of overexertion?
Signup and view all the answers
What was the pediatrician's immediate response to Hassan's worsening symptoms during the second visit?
What was the pediatrician's immediate response to Hassan's worsening symptoms during the second visit?
Signup and view all the answers
Which of the following is a common characteristic of acute lymphoblastic leukemia (ALL) as explained by the oncologist?
Which of the following is a common characteristic of acute lymphoblastic leukemia (ALL) as explained by the oncologist?
Signup and view all the answers
What condition might lead to increased fatigue and anemia in patients with acute lymphoblastic leukemia?
What condition might lead to increased fatigue and anemia in patients with acute lymphoblastic leukemia?
Signup and view all the answers
What diagnostic tests were ordered to assess Hassan's health condition?
What diagnostic tests were ordered to assess Hassan's health condition?
Signup and view all the answers
What was the primary concern that led to the referral to a pediatric oncologist?
What was the primary concern that led to the referral to a pediatric oncologist?
Signup and view all the answers
How did the oncologist describe the behavior of the abnormal lymphocytes in patients with ALL?
How did the oncologist describe the behavior of the abnormal lymphocytes in patients with ALL?
Signup and view all the answers
What symptom prompted Hassan's mother to take him back to the pediatrician a second time?
What symptom prompted Hassan's mother to take him back to the pediatrician a second time?
Signup and view all the answers
Study Notes
Microbiology: Basic and Clinical Principles - Chapter 12
- Adaptive immunity is the body's third and final line of defense
- It engages when innate first- and second-line defenses fail
- It is a set of acquired defenses, responding to specific antigens and establishing immunological memory
Adaptive Immunity Differences from Innate Immunity
- Adaptive immunity takes longer to mount a response (days to weeks)
- Primary exposure response is slow
- It is specific to particular antigens
- Adaptive immunity has immunological memory where secondary exposure to antigens is rapid and effective
Adaptive Immune System Structure
- Subdivided into two highly-dependent branches:
- Cellular response (T cell-mediated immunity)
- Humoral response (antibody-mediated immunity)
- Both branches aim to eliminate the antigen and remember it for quicker responses in the future
Adaptive Immune Response Stages
-
Stage 1: Antigen Presentation
- Dendritic cells and other antigen-presenting cells (APCs) process antigens
- APCs present antigens to T cells
- B cells can directly interact with antigens without APCs
-
Stage 2: Lymphocyte Activation
- Lymphocytes are activated by cytokines (signaling molecules) after successful antigen presentation
- Activated T cells influence B cell activation
-
Stage 3: Lymphocyte Proliferation and Differentiation
- Activated B and T cells undergo multiple rounds of cell division, called clonal expansion
- Some cells differentiate into effector cells which actively fight the antigen, while others become memory cells to quickly respond in future encounters
-
Stage 4: Antigen Elimination and Memory
- Cellular and humoral responses collaborate to eliminate the antigen
- Effector cells die off after the threat is eliminated
- Memory cells remain in lymphatic tissues for rapid response to future encounters with the same antigen
T Cells and B Cells
- T cells and B cells are crucial adaptive immunity leukocytes (lymphocytes)
- T cells originate in the bone marrow and mature in the thymus
- B cells originate and mature in the bone marrow
- Mature B and T cells reside primarily in lymphoid tissues at low levels in circulation
T Cells and B Cells Structure
- T cells and B cells have thousands of receptors on their surfaces; each recognizes a specific epitope
- These receptors are "monospecific"-that is, they only recognize a specific epitope but the body makes diverse types of receptors
T Cells and B Cells Functions
- T cells have roles in both humoral and cellular branches
- B cells coordinate the humoral response by making antibodies
- Our immune system generates a wide array of both T and B cells with the capacity to recognize almost any antigen
Immunogenicity
-
Antigens are any substance triggering an immune response if presented in the correct context
-
Mostly proteins or polysaccharides
- Proteins are predominantly produced by virus, bacteria, and fungus -Also abnormal proteins produced by cancer cells that may also be antigens
-
Cancer cells also frequently produce proteins, and/or polysaccharides
-
Immunogenicity is affected by size, complexity, and composition
- Proteins are usually more immunogenic than lipids and polysaccharides
-
Haptens are incomplete antigens, needing linkage to a complex protein or polysaccharide to trigger an immune response
Antigen Features
- Epitopes are parts of an antigen that B and T cells recognize
- T cell receptors (TCRs) are involved in antigen recognition by T cells
- B cell receptors (BCRs) are associated with antigen recognition by B cells
T Cell Subclasses
-
Helper T cells (TH cells): Most numerous type, releasing cytokines stimulating and coordinating immune responses
-
Cytotoxic T cells (Tc): Directly destroying infected, damaged, foreign, or cancerous cells
-
Regulatory T cells (Treg): Controlling the function of other immune cells
T Helper 1 (TH1) cells:
- Support the cellular response by activating T cytotoxic cells, macrophages, and natural killer cells primarily engaging with intracellular pathogens
T Helper 2 (TH2) cells:
- Support the humoral response by activating B cells to produce antibodies promoting the elimination of extracellular pathogens
Regulatory T cells (Treg):
- Control the functions of other immune cells, maintaining immune tolerance
MHCs and Tolerance
- MHC proteins serve as "self-proteins" or human leukocyte antigens (HLAs)
- T cells screened in the thymus ensuring they correctly recognize "self" MHC molecules and do not attack "self" cells
- B cells screened in bone marrow, ensuring antibodies do not attack "self" antigens
T Cells and B Cells Activation
-
T-cells require two signals for activation
- A primary signal based on MHC-antigen interaction with the T-cell receptor (TCR)
- A secondary signal based on co-stimulatory proteins interactions
-
T-independent antigens trigger B cell activation via direct binding to multiple BCRs on the same B-cell, stimulating its proliferation and differentiation into plasma cells and memory cells
Superantigens
- Superantigens are exceptionally potent T helper cell activators
- Directly crosslink MHC II with the T helper cell TCR
- Triggering a massive, non-specific stimulation of T cells and a release of cytokines, causing potential shock in the body
Effector and Memory T Cells
- Effector T cells eliminate antigens when the threat subsides (die off)
- Memory T cells, long-lived, remain in lymphatic tissues, enabling a swift response to subsequent exposures
MHC I
- All nucleated body cells have MHC I
- Display intracellular antigens to cytotoxic T cells
MHC II
- Only antigen-presenting cells (APCs) have MHC II
- Display extracellular antigens to helper T cells
Humoral Immunity
-
Involves B cells producing antibodies
- T dependent activation via multiple signals for B cells
- T independent activation via direct multiple BCR binding to antigens
-
The antigen binding region is termed variable
-
Isotype Switching: altering the class of antibody produced by the plasma cell but not changing the antigen the antibody recognizes
-
5 antibody isotypes: IgG, IgA, IgM, IgE, IgD
-
Each antibody isotype has specific specializations and predominates in different areas of the body (e.g., blood, secretions, mucosal membranes)
-
Antibody Structure
-
Antibodies ('immunoglobulins') have a monomeric structure with two heavy and two light chains held together by disulfide bonds to form a 'Y' shape.
-
Antigen-binding sites - Located on varying regions - are for precise antigen recognition
Antibody Function
- Antibodies neutralize pathogens (block toxins)
- Activate complement (cytolysis, inflammation, opsonization)
- Increase phagocytosis (via precipitation, agglutination, opsonization)
Immunological Memory
-
Created when memory cells are created - and are responsible for fast and amplified response to future encounters
-
Important for generating quick high antibody titers to specific antigens.
-
Serological testing measure antibody titers (antibody levels in the blood) to determine exposure history (disease, vaccine).
Four Classes of Adaptive Immunity
- Naturally acquired active immunity: Results from contracting an infection
- Artificially acquired active immunity: Results from vaccinations
- Naturally acquired passive immunity: Antibodies pass from mother to offspring (e.g., across placenta)
- Artificially acquired passive immunity: Antibodies are administered as a treatment (e.g., antiserum)
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Test your knowledge on antigens and their characteristics in this immunology quiz. Explore concepts like epitopes, incomplete antigens, and the factors influencing immunogenicity. Challenge yourself with specific examples and key definitions.
