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i have a question regarding helper t cells. It ll be great if someone can kindly help me understand whats going on here:
EXOGENOUSLY SYNTHESIZED PROTEINS are presented on APCs with MHC-II to the Th cells.
Now the Th1 cells respond to INTRACELLULAR PATHOGENS and activates: Tc cells, NK or macrophages.
My question is, if helper t cells respond to exogenously synthesized proteins (and Tc to endogenous), then how can an intracellular pathogen (to which Th1 respond) make an Exogenous protein in the first place? If the protein is synthesized exogenously, shouldn't the organism remain extracellular?
my understanding on the t cell pathways is:
mature naive CD4+ t cell --> encounter apc with mhc-II and exogenously synthesized peptide --> priming of CD4+ cells---> change into effector cells (type depending on nature of signal) :
Th1 if intracellular pathogen (hence, the above question that if the pathogen is intracellular why would its peptide synthesis be exogenous) OR Th2 if extracellular pathogen
Th1 cells then recruit: nk cells, cytotoxic t cells or macrophages for cel medated killing (kaplan immunology pg 89, 1st paragraph). BUT according to FA and in later pgs of kaplan too, IL-12 is produced by macrophages which induces differentiation of T cells into Th1 cells :S :S
so which way is it? macrophages inducing Th1 differentition or Th1 cells recruiting macrophages, Nk cells and Tc cells
These helper T cells are really really reallyyy messing with my head
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