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Helper T cells and their repsonse to antigen

Q: Immunological synapse formation

T cells + antigen-presenting cell make contract rafts (enriched membrane) -> MHC complexes and co-stimulatory receptors clusters toghether form a synapse - These clusters -> supramolecular activation clusters (SMACs) - multiple antigen-presenting cells can bind to a T cell but it will respond to the one with the strongest signal

Q: Helper T cell subpopulations

- Naïve T cells produce IFN-gamma and IL-4 - differentiated ones produce only one of the two - three major populations of CD4 T helper Cells

Q: Memory T cells

- Th1 cells can develop into short lived, IFN-gamma producing helper cells or into long-lived memory cells - central memory cells remain in lymphoid tissue , awaiting invaders - effector memory T cells -> found in inflamed tissue - IL-2 and Il-5 cause memory cells to proliferate

6 important questions on Helper T cells and their repsonse to antigen

Populations of lymphocytes with antigen-binding receptors

- helper T cells
- cytotoxic T cells
- regulatory T cells
- B cells

-> Each cell population can trigger an immune response when antigen bind it's specific receptors

T cell antigen receptor

- Gamma/delta type
- alpha/beta type (95%)
- N terminal varies per cell or immunoglobin -> the variable (V) domain
- The other part is the Constant (C) domain
- Two V domains form a groove -> antigens and MHC molecules bind here
- The groove varies among TCRs
- In the V domain -> complementarity determining region (CDR) -> especially variable
- CD3 -> cluster of proteins associated with TCRs, CD4 and CD8
- prescence of CD4 and 8 determines what MHC molecule is recognized
- 4, MHC2 -> helper cells
- 8, MHC1 -> cytotoxic cells

Immunological synapse formation

T cells + antigen-presenting cell make contract rafts (enriched membrane) -> MHC complexes and co-stimulatory receptors clusters toghether form a synapse
- These clusters -> supramolecular activation clusters (SMACs)
- multiple antigen-presenting cells can bind to a T cell but it will respond to the one with the strongest signal

Helper T cell subpopulations

- Naïve T cells produce IFN-gamma and IL-4
- differentiated ones produce only one of the two
- three major populations of CD4 T helper Cells

Gamma/delta T cella

- the function differs per species
- when stimulated they secrete IL-17 and IFN-gamma
- activated by IL-23
- major defensive function

Memory T cells

- Th1 cells can develop into short lived, IFN-gamma producing helper cells or into long-lived memory cells
- central memory cells remain in lymphoid tissue, awaiting invaders
- effector memory T cells -> found in inflamed tissue
- IL-2 and Il-5 cause memory cells to proliferate