A4 T cells Flashcards
t cell recognition
life of a t cell
-selected in thymus
-matures and migrates into periphery
-circulates through lymphnodes
-IF recognises antigen, activates acquires effector function
T cell receptor (TCR) structure
2 protein chains paired together
-often α and β
-sometimes γ and δ
variable regions
-recognises diversity
transmembrane with cytoplasmic tail
-signalling upon recognition
why is TCR selection required
generates huge diversity of antigen specific t cells
but not all will be useful
-self recognition
-dont recognise MHC
therefore selection is needed
selection of t cells
selected in thymus
tcr is tested to confirm it works and doesnt recognise self
based on affinity, those with strong affinity are deleted
2 types of useful T cells
CD4 helper t cells
CD8 killer t cells
what does the t cell recognise
antigens
(short peptides from pathogen associated proteins that are generated after phagocytosis)
how are antigens recognised
peptides presented to TCR in contect og major histocompatibilty complex (MHC)
two forms
the two forms of MHC
MHC- CD8 T cells
MHCII- CD4 T cells
what happens if T cell recognises antigen/MHC
-naive antigen specific t cells recirculate looking for phagocytes presenting their cognate antigen
-upon recognition t cell and antigen cell form interaction
-TCR transmits signals and T cell becomes activated
what are the 4 T cell functions
proliferation
effector functions
memory
polarisation
proliferation T cell function
huge diversity means antigen specific t cells are rare
activated t cells are useful so need to proliferate to generate effective immune response
effector functions T cell function
CD4 T cells helper function
CD8 T cells killer function
memory T cell function
key feature of adaptive immune system
vaccines
distinct from innate
components of polarisation of CD4 T cell response
-Th1 secretes IFNg and activates macrophage functions
-Th2 secretes IL-4 and helps antibody production
adaptive immunity advantages
random generation of specificity
-allows lymphocyte population to recognise antigenic peptides from many potential pathogens
-stops pathogens evading immune system