Immunology: Innate and Adaptive Immunity Quiz

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Questions and Answers

Which type of immunity acts as the first line of defense against infectious organisms?

Adaptive immunity

Innate immunity (correct)

Acquired immunity

Cell-mediated immunity

Which cells are primarily involved in the process of phagocytosis?

Mast cells and plasma cells

Neutrophils, monocytes, and tissue macrophages (correct)

B lymphocytes and T lymphocytes

Natural killer cells and dendritic cells

What type of receptors do innate immune cells use to recognize pathogens?

Immunoglobulin receptors

Major histocompatibility complex receptors

Antigen receptors

Membrane receptors including those for mannose residues (correct)

Innate immunity can be characterized by which of the following features?

Chemical and physical barriers and non–antigen-specific cells Signup and view all the answers

Which of the following best describes adaptive immunity?

It is directed by T and B lymphocytes that have been primed. Signup and view all the answers

What type of immune response is NOT primarily mediated by Toll-Like Receptors (TLRs)?

Phagocytosis of pathogens Signup and view all the answers

What role do phagocytic cells play during an inflammatory response?

They ingest and destroy pathogenic organisms. Signup and view all the answers

Which TLR is primarily activated by double-stranded RNA?

TLR3 Signup and view all the answers

Which statement about the recognition molecules of innate immunity is true?

They help recognize pathogens by cells other than lymphocytes. Signup and view all the answers

Which of the following cells are classified as innate lymphoid cells (ILCs)?

Cells that do not have antigen-specific receptors Signup and view all the answers

Which statement about TLRs is correct?

TLRs originate from insect species. Signup and view all the answers

What is the primary role of TLR4?

Detecting Gram-negative bacteria Signup and view all the answers

Which TLR is associated with recognizing profilin from Toxoplasma spp.?

TLR11 Signup and view all the answers

Which of the following TLRs is involved in IFN-α and IFN-β production?

TLR8 Signup and view all the answers

What distinguishes TLR10 from other TLRs?

It has an uncertain ligand. Signup and view all the answers

What do TLRs primarily function in?

Cellular activation by microbial pathogens Signup and view all the answers

Which TLRs are involved in detecting viral products?

TLRs 3, 7, 8, and 9 Signup and view all the answers

What does the acronym PAMP stand for in the context of TLRs?

Pathogen-Associated Molecular Patterns Signup and view all the answers

Which of the following is recognized by TLRs on bacterial cell surfaces?

Peptidoglycan Signup and view all the answers

What is the role of non-TLR adapter molecules in TLR function?

To enhance interactions between TLRs and microbial products Signup and view all the answers

What type of pathogen does TLR4 specifically recognize?

Gram-negative bacteria Signup and view all the answers

Which type of nucleic acid is primarily recognized by TLR3?

Double-stranded RNA Signup and view all the answers

Which TLR is NOT primarily associated with microbial detection?

TLR15 Signup and view all the answers

What motif characterizes the extracellular domain of TLRs?

Leucine-rich repeat motif Signup and view all the answers

Which domain is conserved among TLRs and IL-1 receptors?

TIR domain Signup and view all the answers

What role does LPS-binding protein (LBP) play in the recognition of LPS?

Facilitates the binding of LPS to CD14 Signup and view all the answers

Which accessory protein complexes with the LPS-CD14-TLR4 molecule?

MD2 Signup and view all the answers

What initiates LPS-induced cell signaling?

The formation of the LPS-CD14-TLR4-MD2 complex Signup and view all the answers

What type of protein is CD14?

A plasma protein Signup and view all the answers

What is the purpose of the cysteine-rich motif flanking the leucine-rich repeat motif in TLRs?

To stabilize the extracellular domain Signup and view all the answers

What is produced as a result of the dissociation of LBP upon LPS binding?

Affinity of LPS to TLR4 Signup and view all the answers

Which type of immunity is primarily mediated by T lymphocytes?

Cell-mediated immunity Signup and view all the answers

What is a key characteristic that distinguishes ILCs from T and B lymphocytes?

ILCs lack recombination activating genes (RAGs) Signup and view all the answers

Which immune cell type is responsible for defending against extracellular pathogens?

B lymphocytes Signup and view all the answers

What function does the MHC system serve in the adaptive immune response?

It distinguishes foreign molecules from self-molecules Signup and view all the answers

ILCs are similar to T and B lymphocytes but differ in which aspect?

ILCs do not differentiate into memory cells Signup and view all the answers

Which of the following is NOT a major cell population involved in the immune response?

Natural killer T cells Signup and view all the answers

What type of immunity is mediated by B lymphocytes?

Humoral immunity Signup and view all the answers

In the context of the immune response, what does not apply to ILCs?

They engage in cell-mediated immunity Signup and view all the answers

Which group of ILCs is primarily involved in activating macrophages to kill microbes?

Group 1 Signup and view all the answers

What is the role of IL-4, IL-5, IL-9, and IL-13 from Group 2 ILCs?

Activate goblet cells to produce mucus Signup and view all the answers

Which ILC group contributes to increased resistance to extracellular bacteria?

Group 1 Signup and view all the answers

Which cells are activated by Group 3 ILCs to produce antimicrobial peptides?

Mucosal epithelial cells Signup and view all the answers

What is the main function of increased intestinal peristalsis in relation to helminths?

To expel helminths from the body Signup and view all the answers

What type of pathogens do Group 1 ILCs primarily increase resistance against?

Intracellular microbes Signup and view all the answers

Which effector molecule is most associated with the destruction of mucosal epithelial cells?

IL-17A Signup and view all the answers

What role do antimicrobial peptides play in the immune response?

They inhibit microbial growth Signup and view all the answers

Which cytokine is NOT associated with Group 2 ILCs?

TNF Signup and view all the answers

What is the result of increasing mucus secretion in the presence of helminths?

Trapping and expelling helminths Signup and view all the answers

Study Notes

General Features of the Immune System

The immune system protects against infectious organisms (bacteria, viruses, fungi, parasites) and cancer
Immune responses can cause pathologies, whether normal responses to foreign antigens or from immune system aberrations.
A functional immune system is vital for protection against disease.

Innate Immunity (Nonspecific Immunity)

Innate immunity is the first line of defense
It is non-specific to the antigen, meaning it doesn't target a specific pathogen; lacks memory
It includes anatomic barriers (skin, mucous membranes), physiologic barriers (pH, temperature), phagocytic cells (neutrophils, monocytes, tissue macrophages), innate lymphoid cells (ILCs), and plasma proteins (complement).
Phagocytic cells ingest and destroy pathogens and neutralize toxins
Inflammation involves vascular, permeability, and cellular phases.
Pathogen-associated molecular patterns (PAMPs) are recognized by pattern recognition receptors (PRRs).
Damage-associated molecular patterns (DAMPs) also trigger innate immune responses.

Recognition Molecules of Innate Immunity (Pathogen-Associated Molecular Patterns)

Recognition molecules in innate immunity allow non-lymphocytes to identify pathogens.
These molecules sense microbial structures (PAMPs) and endogenous inflammatory molecules (DAMPs).
Various forms of PRRs include collectins, pentraxins, TLRs, RLRs, and NLRs.
TLRs recognize bacterial products (LPS, peptidoglycan), viral (double-stranded RNA), or fungal (a-glucans) components.

Toll-Like Receptors

TLRs are membrane molecules activated by various microbial pathogens' PAMPs.
These molecules initiate inflammatory responses and link innate to adaptive immune systems.
They vary in cellular expression and signaling pathways.

Adaptive Immunity (Specific Immunity)

Adaptive immunity is a second line of defense, with antigen specificity, diversity, memory.
It includes cell-mediated immunity (T lymphocytes against intracellular pathogens), and humoral immunity (B lymphocytes against extracellular pathogens).
T lymphocytes recognize antigens bound to proteins called major histocompatibility (MHC) molecules.
Two major types of MHC molecules exist (class I and II)
B cells and T cells are main cells of adaptive immunity.

Cells and Tissues of the Immune System: Lymphoid Tissues

Lymphoid tissues are crucial for immune development and adaptive immunity.
They are classified into primary and secondary lymphoid organs.
Primary: thymus, bursa of Fabricius, bone marrow, ileal Peyer's patches, fetal liver. Responsible for antigen-independent T and B cell development.
Secondary: spleen, tonsils, Peyer's patches, lymph nodes. Involved in antigen-dependent immune responses and generating adaptive immunity.
Tertiary lymphoid tissues are functionally equivalent to secondary, and are often located near epithelial surfaces. Examples are mucosal-associated lymphoid tissue (MALTs), gut-associated lymphoid tissues (GALTs).

Antigens

Antigens are recognized and responded to, initiating the immune response.
Include foreign viruses, bacteria, parasites, and fungal proteins.
Antigens are transported to lymphoid organs via lymph or dendritic cells.

Innate Lymphoid Cells (ILCs)

ILCs are a heterogeneous population of cells that are not antigen-specific.
They are involved in defenses against infectious microbes, lymphoid-tissue formation, and tissue remodeling.
They are categorized by cytokine profiles (ILC1, ILC2, and ILC3).

T Lymphocytes

T lymphocytes are small, non-granular cells, comprising ~50-70% of peripheral blood mononuclear cells.
They develop in bone marrow, mature in thymus, and are located in secondary lymphoid tissues (e.g. lymph nodes, spleen).
ILCs, macrophages, and dendritic cells also present antigens to cells.
T cells are classified into CD4+ (helper T lymphocytes) and CD8+ (cytotoxic T lymphocytes).

B Lymphocytes

B lymphocytes constitute ~5-20% of peripheral blood mononuclear cells.
B lymphocyte development occurs in two phases:
- Antigen-independent in primary lymphoid tissues (bone marrow, ileal Peyer's patches).
- Antigen-dependent in secondary lymphoid tissues (spleen, lymph nodes). -B lymphocytes express immunoglobulins (IgM and IgD) on their surface.

Mononuclear Phagocytic System (Monocyte-Macrophage System)

Primarily composed of monocytes (circulating) and macrophages (tissue-based).
Function in immunity, inflammation, and tissue remodeling/repair.
Includes cells like macrophages (e.g. Kupffer cells, microglia, alveolar macrophages, mesangial cells).

Dendritic Cells

A specialized population of antigen-presenting cells that differentiate from the myeloid lineage.
Highly efficient in presenting antigens to T lymphocytes, initiating primary immune responses to protein antigens.

Natural Killer (NK) Cells

Large granular lymphocytes that comprise ~5-15% of peripheral blood mononuclear cells.
Primarily involved in early responses to cancerous and virally infected cells.
Do not have antigen-specific receptors; instead, they exert cytotoxic effects based on activating and inhibitory receptors.

Cytokines: Messenger Molecules of the Immune System

Cytokines are small soluble proteins produced by immune and non-immune cells.
They regulate the immune response, acting locally (paracrine) or systemically (endocrine)
Many have pleiotropic (many targets), redundant, synergistic, or antagonistic effects.

Structure and Function of Histocompatibility Antigens

MHC molecules are key for recognizing self vs. non-self.
They function in antigen presentation to T lymphocytes.
MHC molecules are responsible for the compatibility of transplanted tissues.

Disorders of the Immune System: Hypersensitivity Reactions

Involves inappropriate or misdirected responses to antigens in sensitized hosts.
Classified into types I (anaphylaxis, allergies), II (cytotoxic), III (immune complexes), and IV (delayed-type).

Disorders of the Immune System: Autoimmune Diseases

Characterized by an immune response to self-antigens.
Can be organ-specific or systemic.

Disorders of the Immune System: Immunodeficiency Syndromes

Primary: genetic defects, affecting both humoral and cellular immunity
Secondary: acquired defects resulting from infections, malnutrition, or immunosuppression.

Immune Checkpoints

Immune checkpoint proteins regulate lymphocyte activation.
Tumor cells can exploit checkpoints to evade immune detection (immune evasion).

Amyloidosis

Protein misfolding leads to amyloid fibril formation: deposition as extracellular β-pleated sheets.
Can be genetic (e.g., transthyretin) or secondary (e.g., SAA).

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Description

Test your knowledge on the fundamental concepts of innate and adaptive immunity. This quiz covers key aspects such as the first line of defense, phagocytosis, and Toll-Like Receptors (TLRs). Challenge yourself to identify the roles and characteristics of different immune cells and mechanisms.