T cells Flashcards
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
- antigen recognition of Tfh cell induces expression of CD40 ligand and cytokines
- these work together to activate B-cell
- B-cell proliferates
2 requirements for macrophage activation
- 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
- dev in marrow
- recombination in thymus
- 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
- 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
- dendritic cells take up pathogen
- taken apart in DC
- cut up
- put on MHC in cell
- MHC put on the outside
what is mech of intracellular pathogen
- antigen processed in cell in proteosome
- peptide transported to ER
- bound to MHC in ER
- placed on cell surface with MHC
what is mech of extracellular pathogen
- pathogen endocytosed
- degraded with endolysosome
- MHC is made in golgi and put in vesicle
- pathogen and MHC vesicles combined
- MHC placed on cell surface
3 stages of T=cell maturation in thymus
- gene rearrangement in cortex
- positive selection
- negative selection
what is order of gene rearragment
- D-JB
- V-DJ
- V-Ja
what occurs in double negative stage
- T-cell progenitor rearranges to make TCR
- if TCR made - passes checkpoint
- proliferates and enter double pos. stage
what occurs in double pos. stage
- rearrange again to make CD4 and CD8 receptor
2. pass checkpoint
2 types of screening that double pos. Tcells undergo
- 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
- test for self MHC recognition
- 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
- peptide made from proteins made by DCs
- peptides from cell phaged by macrophages
- 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
- 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
- must find APC
- TCR must bind MHC
- second co-stimulation also required to activate T-cell
