T Cells Flashcards
T Cell Receptor
T Cell must see processed antigen in terms of MHC II
V [betta] rearranges via VDJ 1st goes to surface with surrogate [Alpha Chain]
V [alpha] rearranges via VJ 2nd
Which Cells undergo somatic hypermutation?
ONLY T Cells
What and how does CD4 interact with APC
CD4 binds to MHC II via the Betta-2 domain of MHC II
What and how does CD8 interact with target cell?
CD8 binds to MHC I via alpha 3 domain
Which CD is constitutively expressed on all T Cells?
CD3
CD3 is found on both Cyto T and T helper
CD3 is important for clonal amplification and important signaling molecule for activated T cells
Transition from T0 to T1
APC releases cytokine IL12 when it has bound to Th cell
Th Cell in response to IL12 releases INF-gamma
INF-gamma increases bacterocidal activity of Macrophage
INF-gamma is also class switch factor that tells B cells to produce IgG
Transition of T0 to T2
If APC doesn’t release IL12, T0 produces its own IL4
IL4 acts on itself and causes transformation into T2
T2 then makes even more IL4
IL4 is class switch factor for B cells to make IgE
Journey of Immature T Cell
Immature T Cell leaves the Bone marrow and goes to the thymus
In cortical region, T cell is double negative:
CD4-, CD8-, TcR-, CD3-
In cortico-medullary region, T cell is double positive:
CD4+, CD8+, TcRlow, CD3 low
In medullary region, T cell is single positive
CD4+, TcRhi, CD3 hi or CD8+, TcRhi, CD3hi
Positive Selection
Developing T Cell must interact with MHC and respond accordinly
CD4+ must interact with MHCII with proper binding strenth
Negative Selection
Receptor interaction binding with MHC needs to be just right
Too strong and T cell gets eliminated
AIRE
Autoimmune Regulator
Shuttles peptides of body to the thymus to not react with self tissue.
Hypermutation of T-Cells
DOES NOT EXIST
only B cells undergo hypermutation
If T cells underwent hypermutation it would ruin the process of negative/positive selection.
