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Flashcards in T Cells Deck (15):

MHC I Features

Intracellular pathogens
expressed on all nucleated cells
alpha chain 45kD in three distinct domains
B2 microglobulin 12kD


MHC II Features

Extracellular pathogens
APCs only
alpha chain 33kD
beta chain 28kD


T Cell Receptor

alpha chain has VJ, beta chain has VDJ and variable region, arranged in some way as immunoglobulins


Factors contributing to TCR/Ig Diversity (5)

1. multiple copies of VJD
2. D region can be transcribed in different reading frames
3. imprecise joining may occur during rearrangements of genes
4. nucleotides may be randomly inserted/deleted
5. any alpha chain may join with any beta chain


Medawar and Burnet - 1960 Nobel Prize

Demonstrated acquired immune tolerance - non-identical cattle twins happily carried additional set of red blood cells from their sibling - acquired through shared placenta in the wommb - gradual learning process through embryonic life


Th2 production

IL-4 --> STAT6 --> GATA3 --> Th2


Th1 production

IL-12 --> STAT4 -->T-bet --> Th1


Th17 production

IL-6/IL-23--> STAT3 --> Ror gammat T --> Th17


Treg production

TGF-beta --> STAT5 --> Foxp3 --> Treg


Functions of CD4+ (2)

1. maturation of B cells into plasma cells and memory B cells
2. activation of cytotoxic cells nad macrophages - release of different types of cytokines to facilitate different types of immune responses


Activation of T cell steps (3)

Signal 1: TCR binds to antigen as it is held in the MHC complex on the surface of the APC (stabilised by binding of CD4/8 to MHC)
Signal 2: CD28 (T cell) binds to CD80/86 (B7.1/2) on APC
Signal 3: differentiation controlled by different cytokine release

ALSO PRIMING - cell-cell interactions - transient - hold cells together - LFA-1 on T cell to ICAM-1 on APC


Th 1 cells effector cytokines and functions (3) (generally proinflammatory)

1. IFN-gamma - activates macrophages and B cells
2. IL-2 - stimulates B cell growth
3. TNF-beta - activates macrophages and neutrophils


Th2 cells effector cytokines and functions (3)

1. IL-4 - B cell activation, inhibition of macrophage activation
2. IL-5 - eosinophil growth and proliferation
3. IL-10 - inhibits Th1, inhibits macrophage cytokine release


CD8+ activation(2)

1. Simple activation - interaction with proffesional APC
2. long lasting memory cell production - CD8 t cells primed in the presence of CD4 cells undergo second round of clonal expansion - occurs via CD40L (T CELL) and CD40 on APC-DC cell (licensing) - then activates CD8 T cell


methods of killing by CTL (2)

Fas/FasL interaction
Cytotoxic proteins inside granules (perforin and granzyme)