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Molecular Biology and Genetics
MBG 2040
Tara Abraham

Lecture19Physical and Chemical barriers keep us safe and manage microbes so we are not constantly sickThe immune system comes into play when these barriers are breachedoSystem of organs tissues cells and cell products that work together in concert to recognize and neutralize potentially pathogenic threatsThe Immune SystemAdaptive immune systemInnate immune systemononadaptive nonspecificoPhysical barriersoChemical and cellular responses if barriers breachedComplement system surveillance systemoSet of 30 proteins made by the liver that travel in the blood streamoComplement activationProteolytically cleaved to become activeoC1C9 complement componentsoClassical pathwayoLectin pathwayoAlternative pathwayAssociated with innate immune systemC3C3bBfactor DproperdinC5C5bC6C7C8C9Formation of membrane attack complex in target membranes MACDefensinssmall molecules able to lyse most microbial cells and some enveloped virusesoNeutrophils PMN multilobed paneth cells saliva epitheliaoIn the gut concentration gradient of betadefensins higher in the crypt cells secretion is from the crypts that keep out even normal microbiota1 litre of blood contains 6 billion white blood cellsMyeloid bone marrow stem cells differentiate into phagocyte cellsPhagocytecell that eatsoBacterium absorbed into the cell where it forms a phagosome then binds with a lysosome phagolysosome where it is destroyed and then released outside the cellAs antigen presenting cellsoMacrophages and dendrocytes APCsoProcess the antigens they ingest and display them on their surfaces for TcellsoForm a link between the innate and adaptive immune systemMonocytes differentiate into macrophagesCirculate the blood streamAttracted by chemical signals cytokines to sites where they are neededoOn the way they differentiate into macrophagesINFLAMMATORY RESPONSEMacrophages can engulf the invading organisms and digest them then give off cytokine proteins to inhibit the immune responseThe cytokines can cause the endothelial cells of the blood stream to express specific receptors called selectinsThe selectins will bind to neutrophils in the blood and integrins will also bind to adhesion molecules ICAM1 and VCAM1 on the endothelial cellsBradykinin is released that loosens the endothelial cells such that the neutrophils can squeeze through and help the macrophages
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