11: T Cell Mediated Immunity Flashcards
IL-2
An autocrine survival signal for T cells
IL-2RByc
IL-2 receptor constitutively expressed on mature, naive T cells with low affinity
What happens to the IL-2RByc receptor upon T cell activation
Upregulation of CD25, the a chain of IL-2R -> creates IL-2RaBy receptor with high affinity
What cell type always expresses CD25?
Tregs
Trapping naive T cells in LN
- newly activated T cell expresses CD69 -> binds naive T cell S1PR -> naive T cell sequesters S1PR
- Without S1PR, T cells cant migrate (bc binding S1P in blood/lymph is what helps them migrate)
- This ensures activated T cell has time to provide help to other lymphocytes
- Within 5 days, activated effector cells migrate to periphery
Five major functions of IFN-y
- Stimulates macrophages
- IgG class switching
- Expression of HLA class II Ag presentation
- Upregulation of CD80 (B7)
- Inhibits Th2 and Th17 production
What happens if Th2 is predominant in intracellular microbe response?
Poor disease outcomes
Explain classical macrophage activation
Th1 cell migrates to infection -> samples Ags presented by macrophages -> immune synapse between Th cell and macrophage fully activates macrophage to become a better killer
What do IL-4, IL-5, and IL-13 do from Th2 cells
Inhibit Th1 development
IL-5 function
Increases eosinophil migration/activation
IL-13 function
Increases mucus production in epithelium
What do both IL-17 and IL-22 do?
Stimulate defensin production
IL-17 function
Pro-inflammatory; recruits pro-inflammatory leukocytes
IL-22 function
Protective; promotes regeneration in epithelial barrier to prevent breaks in skin
What specific diseases do Th17 cells play a role in?
RA, MS, IBD, integument pathology, cancers (breast, lung)
What two things are constitutively expressed on Tregs?
CTLA-4, CD25
What does CTLA-4 bind to?
CD80 (B7) on APCs; with a higher affinity than CD28
IL-21
B cell survival, clonal expansion, plasma cell differentiation
Similarities between NK cells and CTLs
- Both kill tumor-transformed cells and virus infected cells
- Both use granzymes/perforin or Fas/FasL induction of apoptosis
Differences between NK cell and CTL killing
CTL: notices altered peptide on class I HLA NK cell: notices decreased display of class I HLA
Where are y/S T cells found?
Epithelial boundaries, especially gut
y/S T cell Ag recognition
Recognizes a limited diversity of peptides, but can also recognize some non-protein Ags because they are NOT HLA restricted
What anti-apoptotic protein is expressed by memory T and B cells
Bcl-2
What type of signaling domain does PD-1 contain?
ITIM
Do memory CD4 and CD8 cells require reactivating?
Yes
Which two cytokines are imperative for memory T cell survival?
IL-7, IL_15
What happens when T cells express increased amounts of PD-1 and CTLA-4
They become exhausted
