43 Immune system 2009

43 Immune system 2009 - Biol 61 The Immune System (Chapter...

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Biol 61 – The Immune System (Chapter 43) 4/20/09-4/24/09 The immune system functions to defend the body from invaders, including bacteria, viruses, and fungi, but it also fights eukaryotic parasites and cancer cells as well. The cells that are involved in the immune response are called leukocytes = white blood cells (they are really colorless), in contrast to erythrocytes = red blood cells. There are 3 parts to the defense of the body: 1) passive defense 2) non-specific immunity 3) specific (acquired) immunity 1) passive defense . This includes skin (tough & resistant with a dead outer layer that makes it tough to infect), the stomach (acidic and unfriendly to many things that might end up there), and mucus membranes (sticky to help capture pathogens, agents of disease) in the sinuses and lungs, for example. You also make defensive proteins like lysozyme in your tears (this protein attacks bacterial cell walls). 2) non-specific immunity . This includes the action of the phagocytic cells , ameoba-like cells that eat anything that is not recognized as self, and the “complement ” proteins. These are called “non-specific” responses because in this type of response the immune system is not reacting to any “specific” type of pathogen (a specific virus like a rhinovirus or rubella, for example), but is reacting to the presence of any kind of invader (any type of bacteria or virus will be attacked this way). 3) specific immune response . This occurs when the body develops an immunity to specific pathogens (a particular species of bacteria or strain of virus), and it involves white blood cells called T cells and B cells (T . With the specific immune response, once you get infected your body remembers how to fight that specific pathogen the next time you are infected. Non-specific immunity We’ve basically already discussed the key features of passive defense, so let’s discuss non-specific cellular immunity in a little more depth. Phagocytic cells, or phagocytes, use phagocytosis to ingest their targets, and this is how they get their name (Fig. 43.3). The major types of phagocytes we will discuss include: macrophages . Macrophages are attracted to damaged cells and chemicals released by bacteria, and they can squeeze through the capillary endothelium to get to damaged or infected tissues. Macrophages are found associated with tissues of the immune system (lymph nodes, the spleen, etc.) and are also found moving through the interstitial fluid between the cells of all your organs and tissues (see the picture of loose connective tissue from Chapter 40). They will recognize and eat a large range of objects, including viruses, bacteria, fungi, cell debris, dust, whatever. They also can play an important role in the specific immune response. dendritic cells
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43 Immune system 2009 - Biol 61 The Immune System (Chapter...

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