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Harrison's Principles of Internal Medicine, 18e
| Part 15. Disorders of the Joints and Adjacent Tissues > Section 1. The Immune System in Health and Disease > |
Chapter 314. Introduction to the Immune System
Sections: Introduction to the Immune System, Further Readings.
Topics Discussed: immune system.
Excerpt:"Monocytes arise from precursor cells within bone marrow (Fig. 314-2) and circulate with a half-life ranging from 1 to 3 days. Monocytes leave the peripheral circulation by marginating in capillaries and migrating into a vast extravascular pool. Tissue macrophages arise from monocytes that have migrated out of the circulation and by in situ proliferation of macrophage precursors in tissue. Common locations where tissue macrophages (and certain of their specialized forms) are found are lymph node, spleen, bone marrow, perivascular connective tissue, serous cavities such as the peritoneum, pleura, skin connective tissue, lung (alveolar macrophages), liver (Kupffer cells), bone (osteoclasts), central nervous system (microglia cells), and synovium (type A lining cells).The pool of effector T cells is established in the thymus early in life and is maintained throughout life both by new T cell production in the thymus and by antigen-driven expansion of virgin peripheral T cells into "memory" T cells that reside in peripheral lymphoid organs. The thymus exports ~2% of the total number of thymocytes per day throughout life, with the total number of daily thymic emigrants decreasing by ~3% per year during the first four decades of life.The TCR for antigen..."
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