Chapter 07: Adaptive Immunity

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Questions and Answers

What distinguishes adaptive immunity from inflammation?

It is specific and has memory. (correct)

It is faster to develop.

It is an immediate response.

It only targets bacteria.

Which type of immunity do B cells primarily mediate?

Cell-mediated immunity

Passive immunity

Humoral immunity (correct)

Autoimmunity

What initiates the adaptive immune response?

The activation of B cells

Cells of the innate immune system (correct)

The production of haptens

The presence of antibodies

What is the key difference between active and passive adaptive immunity?

Passive immunity originates from a donor. Signup and view all the answers

Which statement about antigens is true?

Haptens cannot induce an immune response by themselves. Signup and view all the answers

What characterizes the humoral immune response?

Production of antibodies by B cells. Signup and view all the answers

What is the role of epitopes in the immune response?

They are portions of antigens that antibodies recognize. Signup and view all the answers

Which type of antibody is known for its role in allergic reactions?

IgE Signup and view all the answers

How are antigenic determinants on antigens described?

They are the portions that antibodies bind to. Signup and view all the answers

What is a critical factor in the immunogenicity of antigens?

Molecular size Signup and view all the answers

What is the primary role of IgE antibodies in the immune system?

To defend against large parasitic worms and environmental allergens Signup and view all the answers

Which immunoglobulin is predominantly secreted in bodily fluids to protect external surfaces?

IgA Signup and view all the answers

What process is referred to as central tolerance in B cell development?

The elimination of autoreactive B cells in the bone marrow Signup and view all the answers

Which class of MHC molecules is required for Th cells to respond to an antigen?

MHC class II Signup and view all the answers

What determines the antibody specificity during B-cell development?

Somatic recombination of DNA Signup and view all the answers

What function do T regulatory cells (Treg cells) primarily serve in the immune system?

Regulating immune responses to maintain tolerance Signup and view all the answers

Which type of immune response is typically characterized by the rapid production of IgG antibodies?

Secondary immune response Signup and view all the answers

In the development of T cells, which cytokine is critical for promoting lymphoid stem cell division?

Interleukin-7 (IL-7) Signup and view all the answers

What is the primary function of the T-cell antigen receptor (TCR)?

To recognize and bind to specific antigens presented by APCs Signup and view all the answers

What role do dendritic cells serve in the immune response?

They present antigens to naive T cells. Signup and view all the answers

Study Notes

Adaptive Immunity Overview

Adaptive immunity protects primarily against infectious agents, developing slower than inflammation, being more specific, and possessing memory for long-lived immunity.
Initiation of the adaptive immune response involves innate system cells processing and presenting pathogen antigens to lymphocytes in peripheral lymphoid tissue.
Mediated by two lymphocyte types: B cells for humoral immunity (producing antibodies) and T cells for cell-mediated immunity (directly killing targets or stimulating leukocytes).
Can be classified as active (originating within the host) or passive (obtained from a donor).

Antigens and Immunogens

Antigens bind and react with immune response components; immunogens are antigens that can induce an immune response.
All immunogens function as antigens, but not all antigens are immunogenic.
Larger molecules (proteins, polysaccharides, nucleic acids) are more likely to be immunogenic; molecular size influences immunogenicity.
Haptens are small antigens that become immunogenic when attached to larger molecules.

Antibodies

Antibodies are glycoproteins classified into five types based on structure and function: IgG, IgM, IgA, IgE, and IgD.
Composed of two heavy chains and two light chains, they possess antigen-binding fragments and a crystalline fragment for interaction with complement systems.
Antigenic determinants (epitopes) are specific structures recognized by antibodies and antigen receptors.
Protective functions of antibodies could be direct or involve activation of other innate immune components.
IgE is key in allergic reactions and defense against parasitic worms; secretory immunoglobulin IgA protects external body surfaces through secretion.

Collaboration of B Cells and T Cells

Clonal diversity in B and T cells occurs in primary lymphoid organs (thymus for T cells, bone marrow for B cells) during fetal development, allowing recognition of millions of potential antigens.
Immunocompetent T and B cells move from primary to secondary lymphoid organs for further antigen interaction.
B cells recognize antigens through B cell antigen receptors (BCR), while T cells use T cell antigen receptors (TCR) for antigen recognition.
Somatic recombination in B cells allows for a diverse repertoire of antibodies, but autoreactive B cells are often eliminated to establish central tolerance.

T-Cell Development and Immune Response

T-cell maturation occurs in the thymus, where cytokines promote division and receptor production.
Develop into various types: T-helper (CD4) cells assist B cells, and T-cytotoxic (CD8) cells kill infected or malignant cells.
Antigens often require processing by antigen-presenting cells (APCs) for effective recognition by T cells; these include macrophages and dendritic cells.
Primary immune response, dominated by IgM, precedes a secondary immune response characterized by rapid IgG production.
MHC molecules (class I and II) present processed antigens, determining T cell activation; CD4 cells activate μH class II, while CD8 cells respond to class I.

Key Cell Types and Functions

Th cells include Th1 (activating Tc cells), Th2 (supporting B cell activation), and Th17 (activating macrophages).
Tc cells effectively eliminate infected or cancerous cells.
Accessory molecules CD4 and CD8 facilitate T cell interactions with their respective MHC complexes.
Natural killer (NK) cells share characteristics with Tc cells, targeting cells lacking MHC expression.
Self-antigens are typically non-immunogenic due to peripheral tolerance, preventing immune response against the body's own cells.