Adaptive Immunity Chapter I-III

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Questions and Answers

What is the primary function of the lymphatic system?

  • To regulate blood pressure and heart rate
  • To collect residual fluid, filter pathogens, and return fluid to circulation (correct)
  • To transport oxygenated blood throughout the body
  • To produce red blood cells and store platelets

Which feature allows the adaptive immune system to respond more effectively upon subsequent exposures to an antigen?

  • Memory (correct)
  • Specificity
  • Cytokine production
  • Self tolerance

What is required for self tolerance in the adaptive immune system?

  • Selectively allowing B and T cells to respond to self antigens
  • Activation of all immune cells regardless of specificity
  • Selection of antigen-specific B and T cell repertoires and post-selection regulation (correct)
  • Continuous exposure to non-self antigens

Which type of cell is directly involved in presenting antigens to T cells?

<p>Antigen-presenting cells (APCs) (C)</p> Signup and view all the answers

What role does T cell interaction with B cells play in adaptive immunity?

<p>Somatic hypermutation and isotype switching (C)</p> Signup and view all the answers

What process allows antibodies to better recognize antigens?

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

Which function does NOT represent a role of antibodies?

<p>T cell activation (D)</p> Signup and view all the answers

Which type of T cell is primarily involved in cell-mediated immunity?

<p>Cytotoxic T cells (B)</p> Signup and view all the answers

What is the primary role of lymph nodes in adaptive immunity?

<p>Initiate immune responses (D)</p> Signup and view all the answers

How do NK cells identify infected or transformed cells?

<p>Via antibody bridges (D)</p> Signup and view all the answers

Which type of cell is primarily responsible for mediating adaptive immunity?

<p>T cells and B cells (D)</p> Signup and view all the answers

Which type of antigen recognition is performed by B cells?

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

What is the primary role of T cells in adaptive immunity?

<p>Recognize processed antigens presented by MHC molecules (C)</p> Signup and view all the answers

Which pathway involves the presentation of exogenous antigens?

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

What type of T cell is primarily involved in helping B cells differentiate?

<p>Helper T cell (CD4) (C)</p> Signup and view all the answers

What is a distinguishing feature of adaptive immunity compared to innate immunity?

<p>It is highly specific to particular antigens. (B)</p> Signup and view all the answers

Which of the following is NOT a role of B cells in adaptive immunity?

<p>Directly killing infected cells (B)</p> Signup and view all the answers

What defines somatic recombination in lymphocytes?

<p>The generation of diverse receptor repertoires (D)</p> Signup and view all the answers

Flashcards

Antibody Function

Antibodies have various functions, including opsonization and complement activation, neutralizing toxins, and clearing microbes.

Somatic Hypermutation

Process of modifying antibodies to better recognize antigens.

Antibody Isotype Switching

Change antibody tissue distribution and biological functions.

Adaptive Immunity (Cell Mediated)

T cells kill infected or transformed cells; CD8+ cells are crucial. CD4+ cells release cytokines.

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Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC)

Mechanism where antibodies help other immune cells kill infected cells.

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Lymphatic System Function

The lymphatic system collects fluid from tissues, filters pathogens, and returns it to the bloodstream.

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Adaptive Immunity Specificity

The immune system targets a specific antigen it encounters, not others.

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Adaptive Immunity Memory

The immune system remembers a specific pathogen for faster and stronger response upon re-exposure.

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Self Tolerance

Adaptive immunity doesn't respond to the body's own cells or tissues.

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Key Players Adaptive Immunity

Adaptive immunity involves T cells, B cells, antigen-presenting cells, MHC molecules, and antibodies, among others.

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Adaptive Immunity

An immune response specific to particular antigens, mediated by lymphocytes, unlike innate immunity, which is general.

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Lymphocytes (T & B cells)

Specialized white blood cells that are the key players in adaptive immunity, recognizing and responding to specific antigens.

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Antigen Recognition (B cells)

B cells directly recognize the native form of an antigen.

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Antigen Recognition (T cells)

T cells need antigens presented by other cells (APC), broken down into peptides and combined with MHC molecules.

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Antigen Presentation Pathways

Two pathways - exogenous and endogenous - process antigens into peptides for T cell recognition via MHC molecules.

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Exogenous Antigen Pathway

Antigen pathway that takes up pathogens from outside the cell.

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Endogenous Antigen Pathway

Processing antigens made from inside the cell.

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Helper T cell (CD4)

Assists other immune cells, including B cells.

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Study Notes

Adaptive Immunity I-III

  • Adaptive immunity is mediated by lymphocytes (T cells, B cells, and NK cells).
  • Three different types of lymphocytes
  • B and T cells are antigen-specific with specialized receptors.
  • Receptors are generated by somatic recombination.

Adaptive Immunity I: Key Objectives

  • Distinguish lymphocytes mediating adaptive immunity from natural killer cells, myeloid lineage cells, and other hematopoietic cells.
  • Describe how natural killer cells are linked with adaptive immunity.
  • Differentiate mechanisms of antigen recognition between T and B lymphocytes.
  • Distinguish exogenous and endogenous antigen presentation pathways.
  • Describe the lymphatic system's contribution to adaptive immunity.
  • List key features of adaptive immunity.

Key Cellular Elements of Adaptive Immunity

  • Adaptive immunity is mediated by T cells, B cells, and NK cells.
  • Lymphocytes are part of a larger family of leukocytes (white blood cells).
  • B and T cells are antigen-specific and have diverse, specialized receptor repertoires generated by somatic recombination.
  • Hematopoietic stem cells are found in bone marrow.

Antigen Recognition

  • B cells recognize antigens in their free, native form (direct recognition).
  • T cells recognize antigens (proteins) processed into linear peptides and presented with MHC molecules on antigen-presenting cells (associative recognition).

Two Distinct Pathways

  • Antigen processing pathways are exogenous and endogenous.
  • Two classes of MHC molecules (MHC I and MHC II) exist.
  • Two classes of T cells exist (Helper T cells (CD4) and Cytotoxic T cells (CD8)).

Mechanisms of Adaptive Immunity (Humoral)

  • B cells produce antibodies (humoral immunity) and function as antigen-presenting cells (APCs).
  • Antibodies are antigen-specific receptors on B cell surfaces.
  • The process begins as an intrinsic response, similar to a reflex.
  • With T cell help, B cells differentiate to produce more antibodies, refine antigen recognition, and change antibody function (isotype switching).
  • Immune response involves T-B cell co-operation and coordination.

Antibody Functions

  • Antibody functions include opsonization, complement activation, toxin neutralization, and microbe neutralization.

Mechanisms of Adaptive Immunity (Cell-Mediated)

  • T cells can kill infected or transformed cells exhibiting non-self or altered self-antigens (CD8+ cytotoxic T cells).
  • T cells produce cytokines affecting other cell function (CD4+ T cells).
  • Actions triggered by antigen-specific receptors interacting with MHC/peptide complexes.
  • Natural killer (NK) cells lack antigen-specific receptors but can react to specific antigens through antibody bridges.
  • NK cells mediate antibody-dependent cell-mediated cytotoxicity (ADCC) and release cytokines.

Lymphatic System

  • Immune responses are initiated in lymph nodes via cell-to-cell interactions.
  • Lymph nodes contain antigen-presenting cells that deliver antigens from the periphery.
  • B cells reside in lymph nodes.
  • T cells pass through lymph nodes.
  • Multiple layers and pathways of cooperation are essential for adaptive immune system function.

Lymphatic System (Key)

  • Low-pressure circulatory system collecting residual fluid and filtering pathogens from tissues.
  • Empties into subclavian veins.
  • Consists of lymphatic vessels, lymph nodes, bone marrow, spleen, thymus, and mucosa-associated lymphoid tissue.

Key Features of Adaptive Immunity

  • Specificity: Responds to particular antigens and only that antigen.
  • Memory: "Remembers" antigen for accelerated, stronger responses in subsequent exposures.
  • Self-tolerance: Normally does not respond to self-antigens.
  • Self-tolerance depends on antigen-specific B and T cell repertoire selection and post-selection regulation.

Summary

  • Adaptive immunity involves T cells, B cells, NK cells, antigen-presenting cells, accessory cells, MHC molecules, antibodies, and cytokines.
  • Interactions include T-T cell interactions; T cells-accessory cell interactions; T cells-APC interactions; T cells-B cell interactions; NK cells-Antibody interactions.

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