NATS 1730 Lecture Notes - Lecture 7: Clonal Anergy, Thymus, Immunoglobulin M
17 Dec 2016
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The immune system consists of cellular and molecular components that work together to destroy antigens (ags). Although some ags can stimulate the immune response directly, t cell dependent acquired immune responses typically require antigen-presenting cells (apcs) to present ag-derived peptides within major histocompatibility complex (mhc) molecules. Intracellular ag (eg, viruses) can be processed and presented to cd8 cytotoxic t cells by any nucleated cell because all nucleated cells express class i mhc molecules. However, extracellular ag must be processed into peptides and complexed with surface class. Ii mhc molecules on professional apcs to be recognized by cd4 helper t (th) cells. The following cells constitutively express class ii mhc molecules and therefore act as professional apcs: Monocytes in the circulation are precursors to tissue macrophages. Monocytes migrate into tissues, where over about 8 h, they develop into macrophages under the influence of macrophage colony-stimulating factor (m-csf), secreted by various cell types (eg, endothelial cells, fibroblasts).
