L3 - Peripheral CD4+ T Cell Differentiation Flashcards
Describe the estimated number of naive CD4+ and CD8+ T cells in a mouse with ~60 million naive T cells that are specific for a single peptide antigen
Only 20-200 naive CD4+ T cells and 80-1200 naive CD8+ T cells available to respond to a unique peptide antigen.
However, 200 naive cells produce 10,000 effector cells in only 4 days. This is why the typical time-frame for clearing a viral infection is 4-7 days (necessary lag in expansion of an adaptive immune responsive).
Why is T cell differentiation important?
- Tailors effector mechanisms to pathogens
- Limits collateral damage
- Supports immunological memory
Describe the classification of T cell clones
Once it became possible to clone T cells, it provided enough cells to analyse the patterns in the cytokines that they produce and classify them based on this. T cells with different effector functions will produce different cytokines, for example Th1 cells produce IFN-gamma, whereas Th2 cells produce BSF-1.
List the types of CD4+ cells
T-regulatory cells (natural, induced, Th3), T-follicular helpers (Tfh1, Tfh2), T-effectors (Th1, Th17, Th2)
Describe the effect of the Th1/2 balance on the outcome of disease.
Mice with an enhanced Th1 response due to a trans-gene, are able to better control infection and are therefore more likely to live than those with a lower Th1 response.
Does the antigen itself determine the differentiation of the CD4+ T cell?
No - a T cell with an individual TCR is pluripotent so it can become many different types of CD4 cell
Does the environment the recognition occurs in determine the differentiation of the CD4+ T cell?
In vitro, APC-free activation by antibodies, cytokine cocktails and transcription factors are sufficient in inducing differentiation (recognition + co-stimulation + instruction = differentiation).
In vivo, it is more complex
