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Flashcards in Cell Mediated Immunity Deck (21):

Helper T cell activation

binding of TCR to MHC 2 peptide complex (antigen binding), costimulatory molecules (B7:CD28), cytokines (IL-1, IL-6, TNF alpha) from APC to T cell


What determines T cell specialization

by antigen presented on MHC class 2


TH 1 cells

intracellular pathogens, promotes cell mediated immunity

IFN gamma (inhibits TH2, activates macrophages), IL-2 (turns CD8 cytotoxic), TNF alpha


TH 2 cells

promotes humoral immunity, extracellular pathogen removal

secretes IL-4, IL-5 (activates B cell, promotes class switching)


antibody dependent cell mediated cytotoxicity (ADCC)

NK cells, macrophages and monocytes, neutrophils, eosinophils


Cytotoxic cells (CTL) kill by

kill by perforins, cytokines (TNF), granzymes (serine proteases)

Fas ligand on CTL can interact with Fas on target cell to cause apoptosis of target cell


interleukin 2 (IL-2)

cytokine produced by activated naive T cells to proliferate

proliferation of T cell


interleukin 7 (IL-7)

secreted by APC to ensure T cells survive


LFA-1:ICAM-1 interactions

how T cells initially binds to APC, not involved in the activation of T cell, induces conformational change in APC that prolongs cell to cell contact


what happens when T cell meets non bacterial protein antigen

without bacteria, non bacterial protein will be taken up by macrophage but no B7 will be expressed (unstimulated macrophage). T cell will still bind to MHC presenting non bacterial protein but without co-stimulation, there will be no T cell proliferation/activation


what happens when T cell meets bacteria and non-bacterial protein

results in proliferation/differentiation of T cells specific for nonbacterial protein


What would violate the two signal model for T cell activation

If you have a strong enough signal (MHC binds tightly to TCR) you may not need CD28:B7 costimulation.


How do you turn off T cell response

elimination of antigen, elimination of stimuli, IL-2/IL-2R signaling to proliferate, kill immunoregulatory cells


TNF alpha (tumor necrosis factor)

activates endothelium to induce macrophase binding and exit from blood vessel at site of infection


CD8 T cells effector molecules

perforin, granzymes, granulysin, fas ligand


First Checkpoint (T cell development)

mediated by pre-TCR, beta selection, between double negative and double positive, determined by beta chain rearrangement


Second Checkpoint (T cell development)

mediated by alpha Beta TCR, between double positive and single positive, positive/negative selection



master regulator of T cell activation, synthesized by T cell and binds to B7 with greater affinity removing co-stimulation.


Factors in turning off T cell response

elimination of antigen, elimination of other stimuli, IL-2/IL-2R signaling via T regulatory cells, killing by immunoregulatory cells via Fas-Fas ligand


surface cathepsin B

protects CTL from self destruction after degranulation


proteinase inhibitor 9

serpin that inhibits granzyme B, expressed by CTL, dendritic cells, endothelial cells, some tumors

protects CTL from self destruction after degranulation