ImmuneSystem - Immune System Overview • The immune system...

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Unformatted text preview: Immune System Overview • The immune system is the body’s defense against such things as: – Bacterial infection – Viruses – Fungi – Metazoan parasites – Foreign proteins and peptides – Debris and proteases from dead cells – Cancerous cells Defenses • The immune systems defenses can be divided into: – Innate (nonspecific) defenses – barriers that keep out foreign invaders; mechanisms that destroy invaders in a nonspecific fashion. These are present whether the body has encountered the threat before or not. – Adaptive (specific) defenses – mechanisms that respond to specific threats in a particular way. Require priming by a prior encounter with a threat for maximum effectiveness. Innate Defenses • Innate defenses include: – Surface barriers – skin and mucosae – Defensive cells • Phagocytes • Natural Killer cells – Defensive chemicals – antimicrobial proteins – Inflammation – Fever Surface Barriers • The first line of defense against damage is a barrier between the inside of the body and the environment. • The lumen of the digestive tract and the respiratory organs are all technically outside of the body. • The skin and mucous membranes (and the secretions that they produce) are effective barriers. Skin • The keratinized layers of skin resist acidic, basic, and enzymatic attack by bacteria. • Keratin acts as a water resistant layer. • Stratum corneum sloughs off, taking harmful material with it. • Sebum from hair follicles traps material and prevents it from entering the body. Mucosae • Mucous membranes (mucosae) produce proteoglycan mucins that form mucus when hydrated (combined with water). • Mucus traps material which can then be transported to the exterior by peristalsis or ciliated cells. • Many mucosae also produce acids, digestive enzymes (pepsin, lysozyme), or simply water. Self vs. Non-self • Cell surface markers (primarily glycoproteins) identify cells that are part of the body. • Non-self markers identify foreign material and cells for active immune defense. • Many non-self markers provoke a general, non-specific response. • Some markers provoke an adaptive response to that specific marker. Phagocytic Cells • Phagocytic cells engulf foreign matter and fuse the vacuole with vesicles containing digestive enzymes such as lysozyme. – Monocytes become macrophages when activated and phagocytize bacteria and cell debris. – Kupffer cells in the liver and microglia in the brain are specialized types of macrophages. – Neutrophils are primarily responsible for attacking bacteria. – Eosinophils are involved in attacking parasitic worms. Phagocytic Cells • Phagocytic cells engulf foreign matter and fuse the vacuole with vesicles containing digestive enzymes such as lysozyme....
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This note was uploaded on 04/15/2011 for the course BIOL 2301 taught by Professor Kasparian during the Spring '10 term at North Texas.

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ImmuneSystem - Immune System Overview • The immune system...

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