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2012.03.21 - Bio 1202 Lecture Review Notes.docx

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Biology 1202B
Gardiner/ Murphy

Biology Lecture Review Notes Lecture 10 Immunology  Diseases have been around much longer than humans  Immunology – study of the immune system o Involves 3 lines of defense Physical Barrier  Physical barrier – first line of defense o Many of the body cavities are lined with mucus membranes, which contain environments that are hostile to pathogens  Example: acidic stomach kills most ingested bacteria and breaks down most viruses and if any survive, they are exposed to digestive enzymes and bile in the small intestine  Example: reproductive tract is acidic to prevent pathogen survival o Consists of other physical barriers like skin, ear wax, eye lashes, etc. o Once something enters the body it is much more difficult to deal with and fight Innate Immunity  Innate immunity – second line of defense o Generalized internal chemical, physical & cellular reactions against pathogens that have st survived the 1 line of defense o Reactions typically take a few minutes to occur o Has no memory of previous exposure to specific pathogens and acts the same, regardless of the pathogen o Inflammation - creates an internal condition that inhibits or kills many pathogens o Specialized cells engulf or kill pathogens or infected body cells  Example: macrophages, neutrophils, and complement proteins o Involves the following steps:  A break in the skin introduces bacteria, which reproduce at the wound site  Monocytes (a type of leukocyte) enter the damaged tissue from the bloodstream through the endothelial wall of the capillary  Once in the damaged tissue the monocyte differentiates into macrophages (big eaters)  Macrophage receptors recognize & bind to surface molecules of the pathogens and initiate phagocytosis  Cells have receptors so we can recognize if they are from within the body or foreign  If there is not enough macrophages, they will also secrete cytokines to attract other immune cells  Basically, activated macrophages engulf the pathogens & secrete cytokines and chemokines  Death of cells caused by pathogens at the infection site activates cells that are dispersed throughout the connective tissue (mast cells)  Activated mast cells release histamine which dilate local blood vessels and increase their permeability  Cytokines also make the blood vessel wall-sticky, causing neutrophils to attach  The neutrophils will now be subjected to the bacteria  Chemokines attract neutrophils, which pass between cells of the blood vessel wall and migrate to the infection site  Neutrophils engulf the pathogens & destroy them  Signs of inflammation o Heat, redness and swelling is due to dilation of local blood vessels (macrophage and mast cells release cytokines and histamine respectively) o Pus - composed of mostly dead and dying neutrophils o Pain – caused by the migration of macrophages and neutrophils  Complement system – another nonspecific defense mechanism o Interacting soluble plasma proteins (usually inactive) that circulate in the blood and interstitial fluid are activated when they recognize molecules on surface of pathogens o Some of these c
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