T cell-mediated immunity Flashcards
(47 cards)
what is the most common APCs?
dendritic cells
they must be activated
presentation occurs in secondary lymphoid
how are DCs targeted to lymph nodes?
by CCR7 binding to CCL19 and 21
how do DCs present antigen?
via MHC I and II
why is cross-presentation critical for CD8 T cell activation
so that cells that aren’t infected can still activate T cells by presenting intra celluar antigen
what are the two routes that a naive T cell can enter a draining lymph node?
in the blood
in the afferent lymph coming from an upstream lymph node
why is it important for naive T cells to be in circulation?
because it allows for a high probability of antigen contact
- systemic antigen exposure
- localize activation
what two cells make up the immune synapse?
T cells
DCs
what dictates if a T cell is activated by a DC?
the tightness of binding between the TCR and MHC
T cell activation requires three signals, what are they?
TCR
Co-stimulatory molecules
cytokines
why are the co-stimulatory molecules important?
they signal to the T cell to stay alive
B7 and CD28 are the co-stim signals, which is on the DC and T cell
B7 is on the activated DC
CD28 is on the T cell
what is required for T cell activation?
B7-CD28 bindings
why do the cytokines do to T cells?
propagation and differentiation
IL-2
propagation and differentiation of CD8 and all Th cells
the absence of a co-stimulatory interaction leads to what?
anergy
what are the 5 steps of T cell activation
differentiation clonal expansion changes in surface protein expansion migration to target tissues effector functions
what is an important thing that occurs with T cell activation
up regulation of adhesion molecules
what cytokine drives clonal expansion
IL-2
autocrine signaling
how does IL-2 drive clonal expansion
T cells produce own IL-2, which causes and upregualtion of IL-2 receptor, which then induces proliferation
what inhibits continued T cell activation and proliferation?
CTLA-4
How does CTLA-4 inhibit T cells?
it is expressed on activated T cells
- binds an APC after activation leads to T cell inhibition
- B7 binds CTLA-5 twentyfold stronger than CD28
- *remember T cells DO NOT die after function is performed
what are the two ways to activate naive CD8 T cells?
by autocrine IL-2 or by another CD4 T cell producing IL-2
is there a secondary signal needed for activated T cells to kill and infected cell?
NO
the process is very specific
how to CD8 T cells kill the infected cells?
perforin and granzymes
-causes caspase-mediated apoptosis
