Chapter 3

• Induction of antibodies
• Extracellular bacteria > B lymphocytes > elimination of bacteria by antibodies
• Transferred by serum

• 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

• 1. B-cells
• Antibody factories
• Prevent infection
• Target pathogens/toxins for destruction
• 2. T-cells
• Kill infected cells
• Direct innate and lymphocyte responses

• Secrete their antigen receptor = antibody
• Antigen = antibody generating, target of immune system

• Kill infected cells OR
• Activate other cells to do so
• Do not secrete their antigen receptor

• CD8 T-cell
• Defend against intracellular infection
• By killing infected cells they prevent replication and spreading of infection

• CD4 T cell (co-receptor)
• Defend against extracellular pathogens by enhancing phagocytosis by macrophages and neutrophils
• Help B cells make antibodies

Combining receptors generated by uniquely rearranged segments of DNA andother tricks

Recognized by CD8

Bind to CD4 T cells

• Binding of antibody leads to...
• 1. Neutralization
• 2. Opsonization
• 3. Complement activation
• Ultimately leads to degradatoin by macrophage

• Lysis of infected cells
• Secretion of cytokines (interferon gama)

Activation of other cell types (macrophages and B cells)

• Dendritic cells
• Macrophages
• Circulating mononuclear cells
• B cells

Follicular dendritic cells

• Way antibody reduces infection
• Binding to pathogen to inhibit growth, replication, or interaction with humans cells

• 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