T cells, effector functions and the MHC Flashcards
What are the 2 types of MHC
MHC I-single chain molecule, associates with beta 2 microglobulin, endogenously expressed on nucleated cell
MHC II-alpha beta heterodimer. Expressed on specialised antigen presenting cell (monocytes, macrophages, dendritic cellss, B lymphocytes). Displays peptides derived from exogenous antigens
What does MHC class I do and how does it form
allows immune system to eliminate virally infected cells. . (virus hijacks host’s protein production machinery . host cell uses proteozome to break down all protein currently produced by cell, takes peptides+load into newly synthesised MHC I). MHC I shows samples of all proteins available
How does MHC II form
Dendritic cells take up bacterial antigen by endocytos-, vesicle contains proteolytic enzyme to degrade protein. MHC class II molecules synthesise and assemble at ER, MHC class II migrate vesicle where it fuses with vesicle containing degraded antigen. Peptides loaded to MHC class 2 molecules to display to rest of immubne system
What are the properties of T cell receptors
membrane bound heterodimer, 2 chains joined by disuphide bonds, 2 subtypes alpha beta and gamma delta. Consist of variable and constant domains. TCR undegoes rearrangement from germline before translation
How does gene rearrangement in T cell receptor work
In alpha chain-50 v and 50j and 1 alpha constant region
In beta chain-50 v, 2 d, 13 j and 2 constant regions
Any alpha chain can combine with any beta chain
What are the 2 main classes of alpha and beta T cell
CD8+ T cell attaches to MHC I
CD4+ T cell attaches to MHC II
How is the T cell activated
signal 1==TCR and MHC binding stronngly enough for signalling. Provide specificity T cell immune responsse
signal 2=costimulation provided by APC in form of cell surface molecules. Upregulated on APC by danger signals e.g. infection, inflammation
What does CD8 T cells do
cytotoxic, kills virus infected or cancerous cells
T cell binds to target+activated->secretion of cytolytic cytokines+cell to cell interaction->death.
What does CD4 Th1 do
release interferon gamma to help differention and activation of macrophage
release IL2 to allow CD8 to proliferate and differentiate
What does CD4 Th2 do
Produce IL4 and IL13 to help affinity maturation of antibodies, class switching, differentiation of B cell->plasma cellss IL4 and IL5 activate eosinophil
What does CD4 Th17 do
produce IL17, IL21, IL22
Help epithelium and fibroblasts by promoting secretion of antimicrobial peptide to aid wound healing
Promote maturation of neutrophil and attract by chemotaxis
What does CD4 Treg do
Produce TGF beta and IL10
prevent immunopathology by modulating activity of other immune cells
suppress stimulatory activity of APC
Suppress proliferation of responder cells
suppress cytokine production of responder cells
suppress antibody production from B cells
suppress functions of NK cells and NKT cells
