| Nonspecific immunity uses physicochemical barriers, such as the skin and mucosal epithelia, and their associated secreted products, e.g. sweat, mucus and acid. It also involves inflammatory response. Inflammation is the body's response to injury or tissue damage. Its purpose is to limit, and then repair, the damage brought about by any injurious agent. It involves the interaction of the microvasculature, circulating blood cells, other cells in the tissues, and their secreted products. The cells that line blood vessels, endothelium, play a major role in the vascular effects, such as increased permeability and vasodilatation. The cellular effects involve phagocytic and secretory responses of cells that usually circulate in the blood as well as of some that are tissue-based (Table 36.1).
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