Adaptive Immunity Overview

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Questions and Answers

Which function involves the clearance of toxins and neutralization of pathogens by antibodies?

  • Opsonization
  • Cytokine production
  • Toxin neutralization and clearance (correct)
  • Cell-mediated immunity

What is the primary role of CD8+ cytotoxic T cells in the immune response?

  • Killing infected or transformed cells (correct)
  • Engaging in opsonization
  • Activating the complement system
  • Producing antibodies

Which component of adaptive immunity is primarily responsible for memory and specificity?

  • Cytokines
  • Antigen-presenting cells
  • B and T cells (correct)
  • NK cells

Antibody-dependent cell-mediated cytotoxicity (ADCC) is primarily mediated by which type of cell?

<p>Natural Killer (NK) cells (B)</p> Signup and view all the answers

What is a primary feature of the lymphatic system in relation to adaptive immunity?

<p>Filters pathogenic material and supports immune responses (D)</p> Signup and view all the answers

Which interaction is NOT a part of adaptive immune responses?

<p>B cell-antibody interactions (A)</p> Signup and view all the answers

What characteristic allows the immune system to avoid responding to self-antigens?

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

How do cytokines function in relation to T cells?

<p>Influence the activity of other immune cells (C)</p> Signup and view all the answers

Which component is crucial for presenting antigens to T cells?

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

In which structure does the initiation of immune responses typically occur?

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

Which statement best describes the primary role of B cells in adaptive immunity?

<p>B cells recognize free antigens and produce antibodies. (A)</p> Signup and view all the answers

What is a key difference between the antigen recognition mechanisms of T cells and B cells?

<p>T cells require antigen processing, while B cells can recognize antigens directly. (B)</p> Signup and view all the answers

What characterizes the two pathways of antigen processing for T cell presentation?

<p>Exogenous antigens are derived from outside the cell; endogenous are produced within the cell. (B)</p> Signup and view all the answers

How do natural killer (NK) cells relate to adaptive immunity?

<p>NK cells can contribute to enhancing the overall immune response but are primarily part of innate immunity. (A)</p> Signup and view all the answers

What outcome results from B cell somatic hypermutation?

<p>B cells modify their antibodies to improve antigen recognition. (A)</p> Signup and view all the answers

What role does isotype switching play in B cell function?

<p>Isotype switching changes the class of antibodies produced by B cells. (B)</p> Signup and view all the answers

What is the primary function of T helper cells (CD4)?

<p>To provide assistance and coordinate the immune response. (B)</p> Signup and view all the answers

What distinguishes MHC I molecules from MHC II molecules?

<p>MHC I molecules are found on all nucleated cells; MHC II on professional antigen-presenting cells. (D)</p> Signup and view all the answers

What process allows for the diversity of receptors on T and B lymphocytes?

<p>Somatic recombination. (D)</p> Signup and view all the answers

Which statement about the lymphatic system's role in adaptive immunity is correct?

<p>The lymphatic system helps in the transportation of lymphocytes and antigens to lymph nodes. (C)</p> Signup and view all the answers

Flashcards

Adaptive Immunity

An immune response specific to a particular pathogen, involving lymphocytes (T cells, B cells) and sometimes natural killer (NK) cells.

Lymphocytes

White blood cells that are the key players in adaptive immunity.

Antigen Recognition (B cells)

B cells directly recognize antigens in their native form.

Antigen Recognition (T cells)

T cells recognize processed antigens presented with MHC molecules on antigen-presenting cells.

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Antigen Processing Pathways

Two pathways: exogenous (for antigens from outside the body) and endogenous (for antigens from inside the body).

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MHC Molecules

Protein complexes that present antigens to T cells.

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T cell Types

Helper T cells (CD4) and Cytotoxic T cells (CD8).

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Humoral Immunity

The antibody-mediated response of B cells.

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Antibody Function

Antibodies recognize antigens, help activate other immune cells, and neutralize pathogens.

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Antigen Presenting Cells (APCs)

Cells that display processed antigens, enabling immune system activation.

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Opsonization

The process where antibodies tag pathogens for phagocytosis.

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Complement Activation

Antibodies trigger a cascade that enhances the inflammatory response and pathogen destruction.

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Toxin Neutralization

Antibodies block toxins from damaging cells.

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Microbe Neutralization

Antibodies bind to pathogens, preventing them from infecting cells.

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CD8+ cytotoxic T cells

A type of T cell that kills infected or cancerous cells.

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Cytokines

Signaling proteins that influence other cells.

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Lymphatic System

A network of vessels and organs that filter fluids and transport immune cells.

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Study Notes

Adaptive Immunity: Key Elements

  • Adaptive immunity is mediated by lymphocytes (T cells, B cells, and NK cells)
  • B and T cells are antigen-specific with diverse receptors generated by somatic recombination
  • NK cells, while not antigen-specific, are linked with adaptive immunity, mediating antibody-dependent cell-mediated cytotoxicity (ADCC) and releasing cytokines.

Antigen Recognition

  • B cells recognize free, native antigens directly.
  • T cells recognize processed antigens (proteins broken into peptides) presented on MHC molecules by antigen-presenting cells (APCs). This associative recognition involves information processing.

Antigen Presentation Pathways

  • Two pathways process antigens for T cell presentation:
    • Exogenous: for antigens external to the cell
    • Endogenous: for antigens produced within the cell
  • Two classes of MHC molecules: MHC I and MHC II
  • Two classes of T cells:
    • Helper T cells (CD4+)
    • Cytotoxic T cells (CD8+)

Humoral Immunity (B cell-mediated)

  • B cells produce antibodies (humoral immunity) and act as APCs.
  • Antibodies are versions of B cell surface receptors.
  • B cell response initially resembles a reflex action.
  • With T cell help, B cells:
    • Produce more antibodies
    • Modify antibodies to better recognize antigens (somatic hypermutation/affinity maturation)
    • Change antibody tissue distribution and function (isotype switching)

Cell-Mediated Immunity (T cell-mediated)

  • CD8+ cytotoxic T cells kill infected or cancerous cells displaying non-self or modified self-antigens.
  • CD4+ cells influence the function of other cells through cytokine production.
  • Cell-mediated responses involve interactions of antigen-specific receptors with MHC/peptide complexes.

Lymphatic System

  • The lymphatic system is crucial for adaptive immunity. It's a low-pressure circulatory system.
  • It collects fluid from tissues, filters out pathogens and empties into veins.
  • It includes lymphatic vessels, lymph nodes, bone marrow, spleen, thymus, and mucosa-associated lymphoid tissue (MALT).
  • Lymph nodes are rich in antigen-presenting cells that bring antigens from the periphery. B cells reside there; T cells circulate through.

Key Features of Adaptive Immunity

  • Specificity: Response targets a specific antigen only.
  • Memory: Subsequent exposures trigger a faster and stronger response.
  • Self-tolerance: The system does not respond to self-antigens. Self-tolerance depends on selection of antigen-specific B and T cells and post-selection regulation.

Summary of Interactions

  • Key elements include T cells, B cells, NK cells, APCs, accessory cells, MHC molecules, antibodies, and cytokines.
  • Interactions involve T cell-T cell co-operation, T cell-accessory cell interactions, T cell-APC interactions, T cell-B cell collaborations, and NK cell-antibody interactions.

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