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?

<p>Chemical and physical barriers and non–antigen-specific cells (B)</p> Signup and view all the answers

Which of the following best describes adaptive immunity?

<p>It is directed by T and B lymphocytes that have been primed. (C)</p> Signup and view all the answers

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

<p>Phagocytosis of pathogens (B)</p> Signup and view all the answers

What role do phagocytic cells play during an inflammatory response?

<p>They ingest and destroy pathogenic organisms. (B)</p> Signup and view all the answers

Which TLR is primarily activated by double-stranded RNA?

<p>TLR3 (A)</p> Signup and view all the answers

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

<p>They help recognize pathogens by cells other than lymphocytes. (C)</p> Signup and view all the answers

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

<p>Cells that do not have antigen-specific receptors (C)</p> Signup and view all the answers

Which statement about TLRs is correct?

<p>TLRs originate from insect species. (B)</p> Signup and view all the answers

What is the primary role of TLR4?

<p>Detecting Gram-negative bacteria (D)</p> Signup and view all the answers

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

<p>TLR11 (A)</p> Signup and view all the answers

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

<p>TLR8 (D)</p> Signup and view all the answers

What distinguishes TLR10 from other TLRs?

<p>It has an uncertain ligand. (C)</p> Signup and view all the answers

What do TLRs primarily function in?

<p>Cellular activation by microbial pathogens (C)</p> Signup and view all the answers

Which TLRs are involved in detecting viral products?

<p>TLRs 3, 7, 8, and 9 (B)</p> Signup and view all the answers

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

<p>Pathogen-Associated Molecular Patterns (C)</p> Signup and view all the answers

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

<p>Peptidoglycan (C)</p> Signup and view all the answers

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

<p>To enhance interactions between TLRs and microbial products (C)</p> Signup and view all the answers

What type of pathogen does TLR4 specifically recognize?

<p>Gram-negative bacteria (A)</p> Signup and view all the answers

Which type of nucleic acid is primarily recognized by TLR3?

<p>Double-stranded RNA (D)</p> Signup and view all the answers

Which TLR is NOT primarily associated with microbial detection?

<p>TLR15 (A)</p> Signup and view all the answers

What motif characterizes the extracellular domain of TLRs?

<p>Leucine-rich repeat motif (B)</p> Signup and view all the answers

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

<p>TIR domain (B)</p> Signup and view all the answers

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

<p>Facilitates the binding of LPS to CD14 (D)</p> Signup and view all the answers

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

<p>MD2 (A)</p> Signup and view all the answers

What initiates LPS-induced cell signaling?

<p>The formation of the LPS-CD14-TLR4-MD2 complex (C)</p> Signup and view all the answers

What type of protein is CD14?

<p>A plasma protein (D)</p> Signup and view all the answers

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

<p>To stabilize the extracellular domain (C)</p> Signup and view all the answers

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

<p>Affinity of LPS to TLR4 (C)</p> Signup and view all the answers

Which type of immunity is primarily mediated by T lymphocytes?

<p>Cell-mediated immunity (D)</p> Signup and view all the answers

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

<p>ILCs lack recombination activating genes (RAGs) (D)</p> Signup and view all the answers

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

<p>B lymphocytes (B)</p> Signup and view all the answers

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

<p>It distinguishes foreign molecules from self-molecules (C)</p> Signup and view all the answers

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

<p>ILCs do not differentiate into memory cells (D)</p> Signup and view all the answers

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

<p>Natural killer T cells (A)</p> Signup and view all the answers

What type of immunity is mediated by B lymphocytes?

<p>Humoral immunity (B)</p> Signup and view all the answers

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

<p>They engage in cell-mediated immunity (D)</p> Signup and view all the answers

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

<p>Group 1 (A)</p> Signup and view all the answers

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

<p>Activate goblet cells to produce mucus (C)</p> Signup and view all the answers

Which ILC group contributes to increased resistance to extracellular bacteria?

<p>Group 1 (C)</p> Signup and view all the answers

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

<p>Mucosal epithelial cells (B)</p> Signup and view all the answers

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

<p>To expel helminths from the body (C)</p> Signup and view all the answers

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

<p>Intracellular microbes (D)</p> Signup and view all the answers

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

<p>IL-17A (D)</p> Signup and view all the answers

What role do antimicrobial peptides play in the immune response?

<p>They inhibit microbial growth (C)</p> Signup and view all the answers

Which cytokine is NOT associated with Group 2 ILCs?

<p>TNF (D)</p> Signup and view all the answers

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

<p>Trapping and expelling helminths (C)</p> Signup and view all the answers

Flashcards

Innate Immunity

The body's first line of defense against infection, using physical barriers, proteins (like complement), and immune cells like ILCs and phagocytes.

Adaptive Immunity

Antigen-specific immune response involving T and B cells, activated by innate immunity, to eliminate pathogens.

Phagocytic cells

Immune cells that ingest and destroy pathogens and toxins.

Inflammation

A response to infection or tissue damage, involving recruitment of phagocytes.

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Complement System

A group of proteins that enhance the immune system's ability to fight infections.

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Pathogen-Associated Molecular Patterns (PAMPs)

Components of pathogens that innate immune cells recognize by their receptors.

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NK cells

Natural Killer cells are part of innate immunity.

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Neutrophils, monocytes, macrophages

Major phagocytic cells involved in fighting infection.

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Toll-like Receptors (TLRs)

Mammalian immune system homologues of the Toll receptor in Drosophila, playing a role in both embryonic development and immunity.

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TLR3 activation

Triggered by double-stranded RNA, a sign of viral infection, activating innate immune responses.

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TLR4 activation

Triggered by lipopolysaccharide (LPS), a component of gram-negative bacteria. Activates immune responses.

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TLR7/TLR8 activation

Triggered by single-stranded RNA, a sign of viral infection, initiating innate immune responses.

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TLR9 activation

Triggered by CpG DNA, common in bacteria and viruses, initiating immune responses.

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Innate immune response pathway

Involves NF-κB activation, MAPK activation, cytokine/chemokine production and more, in response to pathogen detection.

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TLR5 activation

Triggered by flagellin, a bacterial protein, initiating innate immune responses.

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TLR recognition

TLRs recognize invading pathogens via signature molecular patterns on the pathogens.

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TLRs

Membrane molecules that activate cells in response to microbes.

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PRRs

Pattern Recognition Receptors which recognize pathogen-associated molecular patterns (PAMPs).

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PAMPs

Molecules on pathogens that are recognized by PRRs.

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LPS

Lipopolysaccharide, a PAMP found in Gram-negative bacteria.

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TLR function

Signal to the host that an infection is present.

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TLR location

Some TLRs are on the cell surface; others are inside cells (endosomes).

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TLR specificity

Depends on interactions between TLRs and adapter molecules.

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TLR types

Different TLRs recognize different pathogen types (bacteria, viruses, fungi).

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TLR Structure

Toll-like receptors (TLRs) have an extracellular domain with leucine-rich repeats and a cysteine-rich motif. They also have a conserved intracellular domain called the Toll/IL-1 receptor (TIR) domain.

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MD2 Role

MD2 is an accessory protein that complexes with LPS, CD14, and TLR4, initiating signaling.

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TIR Domain Function

The TIR domain in TLRs interacts with adaptor proteins, initiating downstream signaling pathways.

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TLR Signaling

TLRs activate signaling pathways leading to the production of cytokines and other immune mediators.

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Cytokine Production

TLR signaling leads to the production of cytokines, which are signaling molecules that regulate immune responses.

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Immune Response Activation

The overall effect of TLR signaling is to trigger the immune response, leading to the elimination of pathogens.

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Adaptive Immune System

A specialized immune response that targets specific pathogens, utilizing T and B lymphocytes. It adapts to recognize and eliminate specific threats.

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MHC System

A complex system in the adaptive immune system that allows the identification of foreign molecules (non-self) by distinguishing them from self-molecules.

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Cell-mediated Immunity

A branch of adaptive immunity that involves T lymphocytes directly attacking infected cells and eliminating intracellular pathogens.

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Humoral Immunity

A branch of adaptive immunity that involves B lymphocytes producing antibodies to neutralize extracellular pathogens and toxins.

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ILCs (Innate Lymphoid Cells)

Cells of the innate immune system that are similar to adaptive lymphocytes in origin, but lack antigen-specific receptors and rely on innate mechanisms.

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RAGs (Recombination Activating Genes)

Genes necessary for the development of antigen-specific receptors in adaptive lymphocytes (T and B cells). ILCs lack RAGs.

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How are ILCs different from Adaptive Lymphocytes?

ILCs, unlike adaptive lymphocytes (T and B cells), do not express antigen-specific receptors. This means they're not programmed to target specific pathogens but instead use innate mechanisms to fight infections.

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What's the role of the MHC system for Adaptive Immunity?

The MHC system enables the adaptive immune system to identify foreign molecules (non-self) by comparing them to the body's own molecules (self). This allows for specific targeting of invaders.

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What are some functions of ILC1?

ILC1 cells primarily fight off viral and bacterial infections by producing TNF and IFNγ, which activate macrophages and enhance cell killing.

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What are some functions of ILC2?

ILC2 cells primarily fight off parasitic worms (helminths) by producing IL-4, IL-5, IL-9, and IL-13, which activate eosinophils and mast cells to expel parasites.

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What are some functions of ILC3?

ILC3 cells primarily fight off extracellular bacteria and fungi by producing LT, TNF, IL-17A, and IL-22. These cytokines activate mucosal epithelial cells to produce antimicrobial peptides, increase mucus production, and enhance intestinal peristalsis.

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How do ILCs help in mucosal defense against helminths?

ILC2 cells produce cytokines like IL-4, IL-5, IL-9, and IL-13, which activate eosinophils and mast cells to kill the parasite. They also increase intestinal peristalsis (muscle contraction) to expel the helminth.

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How do ILCs help in mucosal defense against bacteria?

ILC3 cells produce cytokines like LT, TNF, IL-17A, and IL-22, which activate mucosal epithelial cells to produce antimicrobial peptides and mucus. This creates a barrier against the bacteria.

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What is the role of ILC3 in mucosal defense?

ILC3 cells are crucial in protecting against extracellular bacteria and fungi by activating mucosal epithelial cells to produce antimicrobial peptides and increase mucus production, creating a strong barrier against these threats.

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What are the main groups of ILCs?

There are three main groups of ILCs: ILC1, ILC2, and ILC3. Each group has different functions and produces different cytokines to fight specific threats.

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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.

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