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Adaptive Immunity: Lecture 4 (Perforin-Granzyme Pathway (granzyme (a…
Adaptive Immunity: Lecture 4
Perforin-Granzyme Pathway
perforin
pore forming cytotoxic protein found in granules of cytotoxic T cells and NK cells
granzyme
a serine protease released by cytoplasmic granules in cytotoxic T cells
induces cell death to eliminate cancerous or infected cells
uses an effector cell of the system to actively rupture cell wall of target cell
Antigen presentation
infected dendritic cell migrates to lymph node near
represents virus epitopes in combo with MHC I protein
Helper T cell
has improper immune response due to Th cells lacking assist
Clonal expansion
dendritic cells give second signal and activates cytotoxic T cell to secrete IL-2; which triggers cell division
cell stimulation
daughter T cells activate and produce IL-2 receptor and IL-2
no longer need APC and helper T cell
leave node and ready to attack
synthesis of killing proteins
cytotoxic T cell attaches to target and vesicles release contents
perforin molecules associate into a channel in membrane of infection cell through granzyme enters and activates cell death
forces target cell to commit suicide
the cytotoxic T cell disengages and moves on to another infected cell
CD95 Pathway
for cell-mediated pathway
requires CD95 glycoprotein
in the cytoplasmic membrane of body's cells
CD95L receptor activates Th cells to insert CD95l into cytoplasmic membrane
when the Tc cell comes in contact with its target its activated and binds to target
activates enzymes that trigger cell death to kill target cells
T cell Regulation
body carefully regulates them so it doesn't respond to autoantigens
requires several signals to activate
must be in specific sequence or will not activate
T cell APC interact with synapse the two cell types have chemicals dialogue that stimulate T cell to respond fully to antigen
if T cell does not get required signals it will shut down as a precautions
also modulate cytotoxic T cells by mechanisms
provide one more level of cell-mediated responses
Memory T cells
activated T cells
persist in suspended animation for months or years
become functional immediately
has an enhanced immune response
has a better response the second time because of memory of pathogen or virus