T cell mediated Adaptive Immunity Flashcards
Describe the structure of a T cell
one alpha and one bettas chain
with Cd3 molceucles on either side
What does Double negative mean- T cells
T cell porgentiro when they enter the thymus are negative of rCd4 and Cd8 ( Cd3 and T cell receptor)
what is double positive T cells
T cell is producing both Cd4 and Cd8 cells
Describe the Genes relating to the TCR receptor antigne binding section
VDJ
variable diversity and junction gene segments
VDJ recomibination picks up one version of each gene segments and combines them randomly to make unique T cell receptors
What is postiive selection T cells
id they dont recognise self MHC
moderate strength—> helper T
recognised self antigenw ith weak strenght ( cytotoxic T cell
negative selection of T cells
T cells are destoryed if they react to self antigen ( but a number of self0reacit T cells becoem T regulatory cells)- central tolerance
T cells now only express either Cd4 or Cd8-
What is the AIRE gene
allows thymiust to express proteins normally only fodun in specifrc organs- if T cells recognise these they are destoryed- negative selection
Positive selection vs negative selection
central tolerance
Positive selection- destoryed if cant recognise self MHC
negativ selection- destoryed if recognsie self antigen on MHC
what is Peripheral tolerance? - 4 things
niave T cells remain in lymopahtics- canno t entet tissues whilst it is niave
T reg - suppres T cells which react to self antignes
Anegery ( If T cells keep bidning self antigenw ith no B7 costimualtion-) recognsied this and turns itself off—–> self destruction
what is PD-1 involved in
Prograamed cell death protein, PD-1
causes apoptosis in sefl reactive T cells
but
reduces apoptosis in regulatory T cells
plasya a role in self tolerance
describe the principles activation of T cells
MHC binds to TCR and CD4
Co stimulation ((Cd28 Tcell) binding to B7 (APC)
cytokine sreleased by APc bind to receptors on. T cell (cytpkines)
fate specifuing cytokines are repsonsible for developmemnt of eachs usbset of T cells
what is clonal expansions
differneiated Cd4 T cells can proliferta ein processs known as clonal expansion to carry out their speciifc function
what is the role of IL-2 in Th cell activation
positive feedback mechanims- released by T cell
central to development of adaptive immune system- enhances surivial and proliferation
describe the activation of naive Cd8 T cells
recognise MHC I molecules antigen presntation
TCR binds to MCH I:natigne complex as does CD8
production of IL-2 enough to activate the T cell to beocme a cytotoxic T cell
may need binding of CD4 T helper cell that recognises same antigne to binf to an MHV class II moelcuel on same APC- costimualtion of IL-2 and CD4- promote differntiation into cytotoxic T cell
what is the role of reguklatory T lymphocytes
Cd4 cells - suppressiomn of lymphocytes
What is the Function of Th1 cells
- produce IFn-y
- thsi recutirs pro-inflamamtory blood cells and proteins- macrophages–> destory intracellular micoorganisms
- disease —> autoimmunity, chronic inflaamatio n
what is the function of Th2 cells
produce
IL-2, induce TH cells and TH2 cells
IL-5,- maturation and release of eosinophils- degranulation
IL-13- IgE synthesis
traget parasites like helminths–> allergy
describe the action of Th17
Produce IL-17
act on stromal and epithelila cells to promote neutrophils
extracellular bacteria/fungi
I
Describe the action of Tfh
follicular T helper cells
IL-21, Ifn-y and IL4
found in follicles or secondary lymphoid tissues
activate B cells= seceret antigen
extracellula pathogens
Regulatory T cells
dwon regulate differntiation and proliferation fo other subset of T cells
produce
TGf- B
IL-10
Describe the function of CD8 T cells
kills cells infected with pathognes- viruses
regoncise MHCI antigen complex
bind to TCr and CD8
apoptosis of cell induced- performin , express Fas ligand (upon acitvation express on surface)
IL3 required for CD8 cell to becoem acitvated to Cytoxic T cell
what cytokine is needed for Cd8 cells to become Cytotix T cells
IL-2 (released by Th Cells)
