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ImmunologyParasiteDz

lecture 31 niederkorn

QuestionAnswer
cercaria the larval stage of schistosomes released by snails into fresh water
schistosomula infectious skin stage of schistosomes; arises from cercariae that penetrate the skin
concomitant immunity occurs when immune system is able to fend off a re-infection a specific helminth (like schistosomula) but can't get rid of the worms that are still in the body from first infection
hallmark of helminth infections eosinophilia, elevated levels of IgE
critical period for immune system effect with response to Schistosomes immune system must execute eradication within 24-36 hrs. after 48 hrs they move to mesenteric veins and are impervious to the immune system
process of concomitant immunity hyper IgE after initial infection, armed mast cells and eosinophils. new infection activates mast cells --> degranulation and cytokine storm (ECF) for influx of eosinophils that do ADCC using cationic proteins
ADCC (antibody-dependent cellular toxicity) specific IgE FcR against helminths are bound to eosinophils, whenever they invade and IgE binds the schistosomula, eosinophils can then irreversibly bind & kill
Th2 cells secrete IL-4 and IL-5 for immediate hypersensitivity upon re-infection IL-4 = IgE class-switching IL-5 = eosinophil chemoattractant
primary mechanism of eradication of Toxoplasma killing by activated macrophages that phagocytose IgG-coated Toxoplasma (opsonization)
primary cells for immunity after initial Toxoplasma infection Th1 cells are activated and start secreting IFN-gamma, which activates macrophages
reservoirs for latent Toxoplasma infection cells which do not have MHC class I expression like brain and eye (immunoprivileged sites)
immunity to liver stage of Plasmodium and Toxoplasma infections hepatocytes express Ag on their MHC class I, which is recognized by CD8+ T cells specific for infecting protozoan; IFN-gamma = NO production and killing
Plasmodium: sporozoites vs hypnozoites vs merozoites sporozoites - released from Anopheles mosquito after bite, they home to liver cells; hypnozoites - protozoal form that can be dominant in liver cells for yrs; merozoites - form that is released from liver cells to infect RBCs
immunity to Plasmodium sporozoite stage opsonization and ADCC must occur QUICKLY b/c entire body blood vol passes through liver in minutes and after arriving, they enter and infect quickly
immunity to Plasmodium merozoites that have infected RBCs RBCs express Ag naked on surface (NOT BY MHC class I), opsonization and ADCC in reticuloendothelial system of liver and spleen
clearance of re-infection of Trichinella (or other gut-dwelling roundworm) initial infection stimulates Th2 response that mediates complete clearance the second time around within 7 days
body's immune response/physiological changes as a result of Trichinella infection proliferation of gut mast cells with Trich-specific IgE loaded, hyperplasia of goblet cells and increased mucus secretion with IgA to bind them, dramatic gut motility increase, eosinophilia
how Trichinella larvae in muscle are cleared they can't be cleared, usually cause myositis due to eosinophil infiltrate, eventually larvae are calcified within muscle
mechanisms for parasite escape antigen variation using up to 1000 variable surface glycoproteins + escaping phagosome (both in Trypanosoma!), prevention of phago-lysosomal fusion (Toxoplasma), being impervious to lysosomal enzymes (Leishmania)
example of organ that exhibits Ag mimicry Schistosoma and Plamodium falciparum acquire ABO blood group antigens and MHC antigens thus appearing to be host cells; are weakly immunogenic and impervious to conventional immune effector mechanisms
Th1 cells activate macrophages by releasing IFN-gamma to have protective immunity against protozoa, especially Leishmania
Th2 cells are activated by helminth infections to release IL-4 and 5 for eosinophils to do their work
Th17 cells important in bacterial infections
real cause of river blindness from Onchocerca infection Th2 cell response to larval antigens is toxic to the ocular surface, chronic inflammation damages it
Created by: sirprakes
 

 



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