Chapter 14

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

Chapter 14

Specific Immunity (adaptive

immunity)


Adaptive Immunity

Adaptive immunity includes immunity due to:

Exposure to pathogens

Antibody transfer from mother

Vaccination

Injections of antibodies


Dual Nature of Adaptive Immunity

Humoral immunity involves antibodies produced by

B cells.

B cells recognize antigens by antibodies on the

surface of the B cells.


Cell-mediated immunity involves T cells.

T cells recognize antigens by T cell receptors

(TCRs) on the T cell surface.

Dual Nature of Adaptive Immunity


Antigenic Determinants

Antibodies recognize and react with antigenic

determinants, called , on an antigen.


Antibody Structure


IgG antibodies

Monomer

80% of serum antibodies

Fix complement

In blood, lymph, and intestine

Cross placenta, protects fetus and

newborn

Enhance ;

neutralize toxins and viruses


IgM Antibodies

Pentamer

5-10% of serum antibodies

Fix complement

In blood, lymph, and on B

cells

microbes;

first Ab produced in response

to infection


IgA Antibodies

Dimer

10-15% of serum antibodies

In secretions

Mucosal protection


IgD Antibodies

Monomer

Function not fully understood


IgE Antibodies

Monomer

0.002% of serum antibodies

On mast cells, basophils, and in

blood

Allergic reactions; lysis of

parasitic worms


Activation of B Cells

MHC:


Clonal Selection


Activation of B Cells

T-independent antigen:

Provokes antibody

production without

T cell help.

T-dependent antigen: Requires T cell help


T-Dependent Antigens

Helper T (TH) cell

recognizes antigen

Activated TH cells

secrete cytokines


The Results of Ag-Ab Binding


T Cells

Helper T Cells (also referred to as , or TH ,

cells)

T cell receptors (TCRs): Recognize antigens and

MHC II.


Activation of TH


T Cells

Cytotoxic T Cells (CD8,

TC) can differentiate into

cytotoxic T lymphocytes

(CTLs).

CTLs recognize

Ag + MHC I.

CTLs induce apoptosis

in target cell.


Destruction of infected cell by a CTL


Antigen-Presenting Cells (APCs)

Digest antigen

Ag fragments are

presented on surface of

APC in association with

MHC

B cells

Dendritic Cells

Macrophages


Antigen-Presenting Cells

Activated macrophages:

Macrophages stimulated

by ingesting Ag or by

cytokines.

They have increased

and

capabilities.


Extracellular Killing

Antibody-dependent

cell-mediated

cytotoxicity by:

Natural killer cells

Eosinophils

Macrophages


Extracellular Killing

Antibody-dependent cell-mediated cytotoxicity by eosinophils


Immunological Memory

Antibody is the amount of Ab in serum.


Humoral and Cell-Mediated Immune System

Chapter 14

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