Helper T Cells Flashcards
How do T helper cells initiate an immune response?
by secreting multiple cytokines, dividing, and differentiating
Adaptive Process
- Antigen is captured and processed
- antigen is presented to helper T cells together with appropriate co-stimulation
- helper T cell produces multiple cytokines that determine the nature of the immune response
- Helper T cell then acts with antigen to turn on either B cell or effector T cells and generate memory cells
T cell surface markers
TCR- alpha and beta and gamma and delta
What do alpha beta express?
CD4 or CD8
CD4 cells
T helper cells`
CD8
cytotoxic effector cells
Components of a T cell antigen receptor peptide chain
- a variable domain
- a constant domain
- a transmembrane domain
- an intracellular domain
Where is the antigen binding site of a T cell antigen receptor?
between the two variable domains
TCR signal transduction component
called CD3. Consists of multiple paired peptide chains denoted by Greek letters
Signals to the T cell
antigen dose, contact time, degree of co-stimulation
Conversation between antigen presenting cells and T helper cells
- antigen binding to the TCR induces CD154 expression
- CD154 binds to CD40 on the antigen-presenting cell
- CD40 induces expression of CD80 and CD86
- CD80 and CD86 bind first to CD28 and so activate T cells
- As the response progressed they bind to CD152 and turn the response off
What determines the polarization of T cells?
different cytokine mixtures produced by antigen-presenting cells
Paracrine Effect
- T cell activation by antigen and costimulator
- secretion of IL-2
- Expression of IL-2Ralpha chain; formation of high affinity IL-2Ralphabetagamma complex
- IL-2 induced T cell proliferation
Th1 cells
generated by exposure of IL-12 and IFN gamma. Release IL-2 and IFN-gamma. Mediate Type 1 responses
Type 1 Responses
CD8+ T cell-mediated cytotoxicity and macrophage activation
Th2 Cells
generated by exposure to IL-4, TSLP, and IL-33. Release IL-4, IL-5, IL-9, and IL-13. Mediated type 2 responses
Type 2 Responses
immunoglobulin production and IgE-mediated allergic responses
Th17 Cells
generated by exposure to TGF-beta and IL-6 cause Th17 cell differentiation. They are further activated by IL-23 and IL-21. Produce IL-17 and IL-22. IL-17 stimulates neutrophil accumulation and the development of inflammation
What do Th1 cells defend against?
intracellular pathogens
What is Th1’s defining cytokine?
IFN-gamma
What is the principal target cell of Th1?
macrophage activation
What is Th1’s role in disease?
autoimmunity, chronic inflammation
What are Th2’s defining cytokines?
IL-4, IL-5, and IL-13
What is the principal target cell of Th2?
eosinophils
What are the major immune reactions of Th2?
eosinophil and mast cell activation, alternative macrophage activation
What do Th2 cells defend against?
helminths
What is Th2’s role in disease?
allergy
What are Th17’s defining cytokines?
IL-17, IL-22
What is the principal target cell of Th17?
neutrophils
What are the major immune reactions of Th17?
neutrophil recruitment and activation
What does Th17 defend against?
extracellular bacteria and fungi
What is Th17’s role in disease?
autoimmunity and inflammation
Prevalence of delta/gamma T cells
- Humans, mice, and nonruminants- 90-99% use alpha/beta
2. calves, lambs, and piglets up to 66% use delta/gamma
Main cytokine produced by Th1 response
IFN gamma
