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Flashcards in T cells Deck (31):

2 types of T-cells and their functions

CD4 - help other immune cells respond to EXTRAcellular infections
CD8 - kills cells that have become virally infected


what is process of cognate interaction

1. antigen recognition of Tfh cell induces expression of CD40 ligand and cytokines
2. these work together to activate B-cell
3. B-cell proliferates


2 requirements for macrophage activation

1. IFN-y produced by TH1 cell
2. CD40 ligand on T cell binds to CD40 on macrophage


what are 2 T-cell receptors and which is most common

a:B - common
y:d - not sure what it does


what are a:B subdivisions

CD4 and CD8


how does T cell receptor dev.

somatic recombination - V-J rearrangement


where does T-cell stages occur

1. dev in marrow
2. recombination in thymus
3. travel to secondary lymph nodes


how is antigen presented to a T-cell

broken up and put onto an MHC molecule


what is MHC

specialized antigen presenting glycoproteins


what is MHC specificity

can bind multiple different antigens as long as the AA "anchor" is the same


what is T-cell specificity

T-cell can only recognize single antigen and only when bound to MHC


what are 2 classes of MHC molecules, examples, and where found

1. HLA A,B,C - most nucleated cells
2. HLA Ds - only on antigen presenting cells


which MHC correspond to which CD

CD8 - 1
CD4 – 2


how is MHC changeable

MHC is stable and inherited


what is antigen processing

method by which pathogens are broken down to be presented on MHC to T-cell


basic steps to pathogen processing

1. dendritic cells take up pathogen
2. taken apart in DC
3. cut up
4. put on MHC in cell
5. MHC put on the outside


what is mech of intracellular pathogen

1. antigen processed in cell in proteosome
2. peptide transported to ER
3. bound to MHC in ER
4. placed on cell surface with MHC


what is mech of extracellular pathogen

1. pathogen endocytosed
2. degraded with endolysosome
3. MHC is made in golgi and put in vesicle
4. pathogen and MHC vesicles combined
5. MHC placed on cell surface


3 stages of T=cell maturation in thymus

1. gene rearrangement in cortex
2. positive selection
3. negative selection


what is order of gene rearragment

1. D-JB
2. V-DJ
3. V-Ja


what occurs in double negative stage

1. T-cell progenitor rearranges to make TCR
2. if TCR made - passes checkpoint
3. proliferates and enter double pos. stage


what occurs in double pos. stage

1. rearrange again to make CD4 and CD8 receptor
2. pass checkpoint


2 types of screening that double pos. Tcells undergo

1. positive selection - ID cells restricted to self-MHC
2. negative - ID and elim those cells that react to self antigen


2 main functions of pos. selction

1. test for self MHC recognition
2. depending on class of MHC recognized, will tell whether is a CD4 or CD8 - will stop expressing non-binding co-receptor


3 things that are presented to T-cell in negative selection

1. peptide made from proteins made by DCs
2. peptides from cell phaged by macrophages
3. soluble proteins taken up by extracellular proteins


how does T-cell get tested for self-antigen binding

AIRE - transcription factor that causes several hundred tissue specific genes to be transcribed by sub-population in thymic medulla
- bound to MHC 1 for help with negative selection


what are problems with central tolerance

1. some self-peptides not found in thymus
2. this means these won't be negatively selected


what does thymic selection do

give each person and unique T-cell repertoire


how do mature T-cells know where to go

can go to node from lymph or blood vessels – chemokines


what happens when a T-cell encounters its antigens

proliferates and becomes an effector t-cell


how is T-cell activated

1. must find APC
2. TCR must bind MHC
3. second co-stimulation also required to activate T-cell

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