Mechanisms of Innate Immunity & Antigen Presentation Huan-Yao Lei, Ph.D. Department of Microbiology & Immunology College of Medicine National Cheng Kung University

Summary of Chapter 6 Mechanisms of innate immunity Innate immune responses do not depend on immune recognition by lymphocytes The body's responses to damage include inflammation, phagocytosis, and clearance of debris and pathogens, and remodeling and regeneration of tissues. The phased arrival of leukocytes in inflammation depends on chemokines and adhesion molecules expressed on the endothelium. Leukocyte migration to lymphoid tissues is also controlled by chemokines. Plasma enzyme systems modulate inflammation and tissue remodeling. Pathogen-associated molecular patterns (PAMPs) are distinctive biological macromolecules that can be recognized by the innate immune system. Microbicidal proteins are part of the innate immune system.

Summary of Chapter 7 Antigen presentation T cells recognize peptide fragments that have been processed and become bound to major histocompatibility complex (MHC) class I or II molecules. MHC class I molecules associate with endogenously synthesized peptides, binding to peptides produced by degradation of the cells' internal molecules. MHC class II molecules bind to peptides produced following the breakdown of proteins that the cell has endocytosed. Cross-presentation allows APCs to acquire antigens from infected cells. Co-stimulatory molecules are essential for T cell activation. CD4 binds to MHC class II and CD8 to MHC class I molecules. The highly ordered area of contact between the T cell and APC is an immunological synapse. T cell activation induces enzyme cascades, leading to the production of interleukin-2 (IL-2) and the high-affinity IL-2 receptor on the T cell. Antigen presentation affects the subsequent course of an immune response.