Immune System: Part 2
Immune System: Part 2 Biol 2312
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This 2 page Class Notes was uploaded by rkl130030 on Saturday April 23, 2016. The Class Notes belongs to Biol 2312 at University of Texas at Dallas taught by Michelle Wilson in Winter 2016. Since its upload, it has received 20 views. For similar materials see Introduction to Modern Biology II in Natural Sciences at University of Texas at Dallas.
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Date Created: 04/23/16
The Immune System: Part 2 Tolllike receptors (TLR) via innate immunity Best studied TLR is Drosophila o Originally discovered as part of the dorsalventral patterning pathway o Responds to fungal infection (TLR) 11 in humans, 13 in mice. Bind to specific targets needed for pathogen survival o Gramnegative LPS o Bacterial lipoproteins o Bacterial peptidoglycan fragments o Yeast cellwall components o Unmethylated CpG motifs in bacterial DNA o Viral DNA Contain leucinerich regions that contour to form binding pocket A singlecell receptor type recognizes a range of pathogens Innate response to infection: o Innate receptors activate > signal transduction pathways turned on > enhance innate and adaptive immune responses > induction of inflammatory response > antimicorbial peptides produced > cytokines produced > attraction of phagocytic cells, B cells, & T cells Second class of receptors discovered (cytoplasmic receptors) o Bind to pathogen molecules o Recognize invading pathogens in the cytoplasm after phagocytosis o Part of response to viral RNA Soluble receptors circulate in serum and respond to specific pathogen molecules Innate immunity = variety of responses to pathogens Several classes of peptides: defensins, interferons, cytokines Defensins: cysteines interact with postiviely charged amino acids on surface of pathogen o Disrupts the membrane and enhances phagocytosis Interferons: Type I and type II secreted signaling molecules o Type I – synthesized when a virus infects a cell and acts as a messenger that protects normal healthy cells close by; induces degradation of RNA and blocks production of protein needed for cells (kills cells, but prevents spread of virus) o Type II (interferon gamma, in humans) produced only by Tlymphocytes and natural killer cells (NKC); secretion is part of defense against infection and cancer Cytokines: attract other nonspecific phagocytic cells, causes inflammation, and signals adaptive immune system Phagocytic cells and innate immunity 3 basic kinds of defending leukocytes: o Macrophages – large, irregularly shaped, kills microorganisms by ingesting them through phagocytosis Can engulf viruses, cell bebris, and dust particles in the lungs Roam around in the extracellular fluid Monocytes squeeze through endothelial cell walls of capillaries in order to enter connective tissue At site of infection, monocytes mature into phagocytic macrophages o Neutrophils – account for 50% 70% of peripheral blood leukocytes First type of cell to appear at site of infection/damage Squeeze through capillary walls like macrophages Produce a large range of reactive oxygen radicals and defensine peptides o Natural Killer Cells kill cells that have been infected with virus by inducing apoptosis of targeted cells Perforins insert into the membrane and create a pore, which allows granzymes to enter membrane and activate proteins that induce apoptosis Attack tumor cells mainly before the cells have had a chance to divide and create a tumor (most potent defense against cancer) Inflammatory response to infection/tissue injury Can be either localized or systemic Acute response: starts rapidly and lasts for a relatively short amount of time Chemical alarm signals released (histamine, prostaglandins, bradykinin) cause vasodilation and induce edema by by increasing permeability of capillaries o Increased blood flow to area causes warmth and redcoloring o Swelling puts pressure on nerveendings, which leads to pain and some loss of function Pus is a mixture of dead/dying pathogens, tissue cells, and neutrophils Acutephase response: increased body temperature (ILI causes neurons in the hypothalamus to raise body temp several degrees above normal Fever causes the liver and spleen to store iron; this reduces the blood level of iron, that of which bacteria needs in order to grow o Excessive heat can denature critical enzymes, causing high fevers to be hazardous Complement system A group of approximately different proteins that circulate freely in blood plasma Usually occur in innactive form and enters tissues during inflammatory response Activated by mannosebinding lectin protein (MBL) or by a complex series of reactions that involve charged species on the surface of pathogens
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