Cellular Immunity Flashcards
How are antigens taken to lymph node
When there is injury, dendritic cells take up and move to lymph node via lymphatic system
Nonbacterial vs bacteria engulfment by macrophage
Bacteria - PRRs stimulated, B7 expression induced, signal 2 delivered, T cells activated
3 signals
Activation - this is MHC/TCR interaction with CD4 or CD8
Survival - This is coreceptor B7 interacting with B7
Differentiation - production of cytokines from APC to the T cell
Dendritic cell in tissue vs. lymph node
In tissue - highly phagocytic, lower MHC expression, B7 not expressed, Ag presentation low
Where do lymph nodes receive lymphocytes?
From bloodstream and affarent lymphtics (coming from other lymph nodes)
Those T cells that don’t have correct TCR will
Leave through efferent lymphatic vessel to next lymph node
T cells that do have correct TCR
Will stay in lymph node to proliferate
How do naive T cells enter secondary lymphoid tissues?
Non-specific cell adhesion molecules
Diapedesis
once in the secondary tissues, what do naive T cells do?
Bind to APCs via integrins and Ig superfamily molecules…this allows TCR/MHC interaction
What is co-inhibitory mechanism
B7 from APC binds CTLA-4 on the T cell
CTLA-4 binds with higher affinity than CD28
pSMAC and cSMAC
pSMAC has adhesion molecules needed to attach T cell to Dendritic
cSMAC has CD markers and TCR
TCR signaling leads to which TFs
NFAT, NFkB, and AP-1…leads to IL-2 transcription
Cyclosporine A
Block NFAT activation
Naive T cell TCR vs. mature
Naive - has gamma and beta subunit but not alpha…binds IL-2 with lower affinity
End result of IL-2 binding
Secretion of more IL-2 and porliferation
CD4 helper T differentiation
All these from dendritic cells
IL12 - Th1 - Cytotoxic
IL4 - Th2 - humoral
IL23 - Th17 - Inflammation
TGFB - Treg (tones down T cell response)
Antigen-specific T cell locations
Exposed and trapped in lymph node for a period of time where they won’t be found in efferent lymph
CD8 (CTL) cells
Need CD3, CD8, alpha, beta, and T cell to work
Positive and negative selection in thymus
Clonal proliferation…helped by CD4s that secrete IL-2
CTL mediated killing
Rapid Cell-cell contact Apoptosis of target Killer T can affect multiple targets Bystanders unaffected
3 steps to CTL killing
Target cell binding
Programming target for lysis (Ca dependent)
Death
Perforin
Aids in delivering contents of granules into the cytoplasm…forms pores allowing passage of granzyme
Granzyme
Serine proteases that activate apoptosis in the cytoplasm of target cell
