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
