T cells Flashcards
Define cluster of differentiation
a defined subset of epitopes that identify cell type and stage of differentiation, and which are recognised by antibodies
Are CD exclusive to leukocytes?
No, specific CD groups have been identified on other cell types
Which CD associates with the T-cell receptor?
CD3, forming the TCR-CD3 complex. CD3 participates in signal transduction when a T cell interacts with an antigen
What 5 chains make up CD3?
heterodimer gamma-epsilon chains, heterodimer epsilon-delta chains, and homodimer zeta-zeta chain
What other molecule plays an important role in signal transduction?
ITAMs when they interact with tyrosine kinases
What are the 4 subclasses of CD4 T cells?
Th1, Th2, Th17, and Treg
When do CD4 T cells differentiate into their 4 subclasses?
during the progression of an infection
What affects which subclass is made?
depends on the effects of the infection on APC (ie. dendritic cells)
What is the function of Th17?
it is the first effector T cell to be generated
it secretes IL-17, which stimulates local cells to secrete other cytokines & chemokines
chemokines attract neutrophils and cytokines will help express antimicrobial peptides by effector cells
What is the difference between Th1 and Th2?
if the route of entry or physical form of the antigen favours macrophage activation, then there is a Th1 response
soluble antigens and/or infections of the mucosal sites favours a Th2 response
What cytokines activate differentiation into Th1 or Th2?
Antigen-activated naïve CD4 T cells produce IL-2.
If they proliferate in a IL-14 environment, they generate Th1
If they proliferate in a IL-4 environment (presence of mast cells or mucosal infection), they generate Th2
What CD molecule is found on Treg cells taht is not found on other CD4 T cells?
CD25, the receptor for IL-2, which signals the cell to start division
What is the function of Treg cells?
They regulate cell division, so the proliferation of other T cells, control autoimmunity, tolerance
Which cells generate Treg cells?
thymocytes, found in the thymus, in the presence of Foxp3 (a transcription factor)
What is the connection between Treg cells and Th17 cells?
in early infection, differentiation of naïve CD4 T cells shifts from Treg to Th17, leading to acquired immunity mechanisms
