M1 and M2 Macrophages: Oracles of Health and Disease

The purpose of immunology is simple. Cure or prevent disease. M1/M2 is useful because it is simple. M1/M2 describes the two major and opposing activities of macrophages. M1 activity inhibits cell proliferation and causes tissue damage while M2 activity promotes cell proliferation and tissue repair. Remarkably, the molecules primarily responsible for these "Fight" (NO) or "Fix" (Ornithine) activities both arise from arginine, and via enzymatic pathways (iNOS and arginase) that down regulate each other. The names M1 and M2 were chosen because M1 and M2 macrophages promote Th1 and Th2 responses, respectively. Products of Th1 and Th2 responses (e.g., IFN-γ, IL-4) also down regulate M2 and M1activity, respectively.…

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