The document summarizes the key aspects of specific or acquired immunity: 1. There are two main types of acquired immunity - natural and artificial. Natural immunity develops after exposure to pathogens while artificial immunity involves vaccination. 2. Both natural and artificial immunity can be active, involving the production of antibodies, or passive, involving the transfer of existing antibodies. Active immunity is usually longer-lasting while passive immunity is temporary. 3. Acquired immunity involves both humoral immunity mediated by antibodies from B cells and cell-mediated immunity carried out by T cells that target infected cells. Together these adaptive immune responses provide specific protection against pathogens.

1. Specific Host Defenses : Adaptive Immunity ACQUIRED or SPECIFIC IMMUNITY

2. Two major kinds of defense Innate immunity Acquired immunity

5. Types of Acquired Immunity Acquired Immunity

12. Humoral Response to T Independent Antigens Cell growth division, and differentiation in a lymph node Clone of many effector cells secreting antibodies ER ER ER ER Selection of B cells Triggering of the B cell

13. Humoral Response to T Dependent Antigens

18. PRIMARY RESPONSE (initial encounter with antigen) Antigen Antigen receptor on a B cell Antigen binding to a B cell Memory B cell Antibody molecules Plasma cell Cell growth, division, and differentiation SECONDARY RESPONSE (can be years later) Cell growth,division, & further differentiation Larger clone of cells Plasma cell Antibody molecules Later exposure to same antigen Memory B cell Clone of cells

21. Antibody Response After Exposure to Antigen

24. Acquired Immunity: Ag-Specific Responses

25. T Lymphocytes: Cell Mediated Immunity Figure 24-16: T lymphocytes and NK cells

27. T Cells Only Recognize Antigen Associated with MHC Molecules on Cell Surfaces

30. APC = e.g., Macrophage TCR Peptide Antigen CD4 CD4 T Cell MHC Class II

32. Central Role of Helper T Cells

36. The big picture…Integration of innate and adaptive immunity Courtesy: Abbas and Litchman; Basic Immunology