Innate Immune System

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Innate Immune System

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University of Southern California
Bisc 307l - General Physiology
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BISC 307L 2nd Edition Lecture 31 Current Lecture Innate Barrier Defenses 1. The skin is a barrier to invasion of the body and infection. The outer layer, the stratum corneum, is very dry and has an acidic pH and is covered with toxic oil as well as sweat, which has antibacterial agents in it. 2. Other epithelia, which are in contact with the outside (including the respiratory or digestive tracts, which are particularly being exposed to pathogenic organisms through inhaled air or particles or food, and the urinary or the genital tracts, which are also subjected to pathogens) will secrete: 3. Mucus, which is sticky to trap foreign matter, contains lysozymes & IgA, and may be moved by cilia. 4. Normal Flora, which are bacteria that have colonized and lived commensally with us to protect the body from pathogens. Immune System Cells Brief overview of all the cells of the immune system. These are all “leukocytes”, or white cells(not white blood cells). White cells can spend all their time in tissues, in blood, or travelling back and forth. The ones that are in the blood most of the time are basophils, neutrophils, eosinophils, monocytes (which differentiate into macrophages). The tissue leukocytes are mast cells, dendritic cells, natural killer cells, and most of the organ-specific phagocytes. A number of these cells are phagocytic. Neutrophils and macrophages are very active phagocytes. Neutrophils have very short lives of a few hours during which time they can ingest 5-10 bacteria, and die. Macrophages live longer and can ingest maybe 100 bacteria before they die. Although they are mainly blood cells, they sometimes travel to the tissue, and this is where they do most of their phagocytosing. Neutrophils will go into the tissue, ingest bacteria, and die. Whereas macrophages will enter the tissue, phagocytose, and possibly move back to the blood. Eosinophils mainly attach to parasitic worms and attack them. Among the lymphocytes, B lymphocytes are phagocytic and have some overlap of function with macrophages. Dendritic cells are very phagocytic cells that are fixed in the tissue. There are three types of Glia in the brain: astrocytes, oligodendrocytes, and microglia. Those are all diverse groups – there are several types of each. Kupffer cells in the liver are a fixed phagocyte. There exist fixed phagocytes in the spleen as well. There are cells called granulocytes from the appearance of granules in their cytoplasm – the granules are vesicles. Neutrophils and eosinophils are considered granulocytes, as are basophils and mast cells. They are very important in inflammatory responses. Lymphocytes – the B type secretes antibodies, and the T type has a number of different functions, one of which is to be cytotoxic and attack and kill other cells directly. And cytotoxic T lymphocytes share a lot in common with the natural killer cells. One of the main differences between them is how they select the targets to kill. The cytotoxic T lymphocytes are part of the specific immune system, and the natural killer cells attack a ...

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