Chapter 3

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Humoral Immunity
- Induction of antibodies
- Extracellular bacteria > B lymphocytes > elimination of bacteria by antibodies
- Transferred by serum
Cell-mediated immunity
- Phagocytosed microbes in macrophage > T cell > activation of macrophage leading to microbial killing
- Virus infected cell > T cell > lysis of infected cel
- Transferred by lymphocytes
Classes of lymphocytes
- 1. B-cells
- Antibody factories
- Prevent infection
- Target pathogens/toxins for destruction
- 2. T-cells
- Kill infected cells
- Direct innate and lymphocyte responses
B cells
- Secrete their antigen receptor = antibody
- Antigen = antibody generating, target of immune system
T cells
- Kill infected cells OR
- Activate other cells to do so
- Do not secrete their antigen receptor
Cytotoxic lymphocytes (CTL)
- CD8 T-cell
- Defend against intracellular infection
- By killing infected cells they prevent replication and spreading of infection
T helper lymphocyte (TH)
- CD4 T cell (co-receptor)
- Defend against extracellular pathogens by enhancing phagocytosis by macrophages and neutrophils
- Help B cells make antibodies
B Cell Receptor
T cell receptor
How is specificity of antibody generated?

Combining receptors generated by uniquely rearranged segments of DNA andother tricks
MHC Class I

Recognized by CD8
MHC Class II

Bind to CD4 T cells
Functional outcome of B cell activation
- Binding of antibody leads to...
- 1. Neutralization
- 2. Opsonization
- 3. Complement activation
- Ultimately leads to degradatoin by macrophage
Function outcome of Cytotoxic T cell activation
- Lysis of infected cells
- Secretion of cytokines (interferon gama)
Functional outcome of T helper cell activation

Activation of other cell types (macrophages and B cells)
Principle antigen presenting cells for T cells
- Dendritic cells
- Macrophages
- Circulating mononuclear cells
- B cells
Principle antigen presenting cells for B cells

Follicular dendritic cells
Neutralization
- Way antibody reduces infection
- Binding to pathogen to inhibit growth, replication, or interaction with humans cells
Opsonization
- 1. Coating it with antibodies
- When coated with IgG anitbodies, they bind to receptors on a phagoctye
- 2. Coating with complement
- Activation of classical pathway of complement activation
- Pathogen becomes coated with C3b > increase phagocytosis by macrophages

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LT24

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Chapter 3

Description

Adaptive Immunity

Updated

2010-01-26T04:37:07Z

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