BIO269 - Immunology - Innate Defenses

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innate defenses

defenses that you're born with and are the same for every human being; can be either surface or internal

surface innate defenses include

the skin and musosae

mucosa

the innermost layer of the intestine, epithelial, a barrier between bacteria and the rest of the body

internal innate defenses include

phagocytes, fever, NK cells, antimicrobial proteins, inflammation

immunology is split into ___ systems:

2; innate, adaptive

adaptive defenses include

humoral immunity (b cell) and cellular immunity (t cell)

how does the integument act as an innate defense?

(1) the fact that its multilayered makes it more difficult for bad things to get through (2) the stratum spinosum secretes keratin to stop bacterial enzymes and toxins

how do epithelial membranes act as innate defenses?

(1) acidic secretions & stomach's acidic mucosa keep the pH low enough that most bacteria won't thrive (2) saliva contains lysozymes to kill bacteria (3) mucus in the respiratory tract traps inhaled bacteria from progressing (4) mucus in the digestive tract retards bacteria's burrowing into the walls

how does phagocytosis work, exactly?

the phagocytic organelle engulfs the target substance and forms a phospholipid membrane (vesible) around it to isolate it; the membranes of the vesible and lysozome bind together to let the lysozome contact the target without exposing the rest of the cell; the lysozome digests it and then fuses with the membrane for exocytosis, where the antigens (end products) are presented to other cells for complete disposal

natural killer cells

lymphocytes (5-10%) that are non-specific sugars, trying to kill anything whose surface doesn't have recognizable proteins

how do natural killer cells work?

when they detect a foreign cell, they attack the cell's membrane releasing perforins, making holes in the membrane; ECF enters, causes it to burst; also causes nucleus to disintegrate if there is a nucleus

signs of inflammation

redness, heat, swelling, pain, impairment of function (immobilization)

the inflammatory process

receptors on the cell surface release chemicals (histamine, kinins) to begin the process, which causes small blood vessels to dilate (redness & heat from more blood to the area) and capillaries to increase permeability, which leads to edema (fluid leaks out via fenestrations to ECF, upsetting its homeostasis with infected cell, so the fluid then goes into the cell) and, thus, pain

how does inflammation aid in the healing process?

the extra fluid dilutes the harmful substances, and the extra blood flow delivers more oxygen and nutrients

what follows inflammation?

phagocyte mobilization

phagocyte mobilization

a process after inflammation that involves a large increase in neutrophil concentration (4-5x), which all aggregate in the blood vessel and marginate (adhere to the wall), leaving via diapedesis and finding the infection via chemotaxis

how do viruses work?

viruses are made up of either DNA OR RNA, plus protein, so they can't self-replicate; they need to use the host's "cellular machinery" (whichever DNA or RNA they're missing)

interferons

antimicrobial proteins that interfere with viral replication

how do interferons work?

the virus enters host cell 1 and starts replicating, triggering the interferon genes; but cell 1 is a lost cause, so the interferons go out into the ECF, where other cells can detect them and start making their own antiviral proteins, which block the virus's access to ribosomes, which they need to replicate; eventually, they die off

how does fever work as an innate defense?

bacteria release exogenous pyrogens (foreign chemicals) which trigger leokocytes to release endogenous pyrogens (familiar chemicals), which trigger the hypothalamus to release prostaglandins, a hormone that causes shivering (targeting skeletal muscle) to increase body temperature, in the hopes that it will go out of the bacteria's operational range; meanwhile, the liver and spleen gather up all iron and zinc, which the bacteria need for replication, and metabolism speeds up

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