2. Venue : B101,Institute of Biomedical Science and Technology
3. Speaker Cheong-Hee Chang
Regulation of adaptive immunity by innate CD4 T cells
Unlike conventional T cells, innate-like T cells that include NKT cells, mucosal-associated invariant T (MAIT) cells, H2-M3 restricted T cells, CD8aa intraepithelial lymphocytes (IELs), gd T cells, and innate CD4 (iCD4) T cells, exhibit a fast and more robust effector function such as cytokine release or cytotoxicity. They also tend to reside in non-lymphoid tissues and to have markers of chronically activated or memory cells. These cells are thought to serve as a bridge between rapidly occurring innate immunity and more slowly occurring adaptive immunity.
iCD4 T cells are selected by MHC class II expressed on hematopoietic cells and they are remarkably similar to NKT cells in their development and function. Unlike conventional CD4 (cCD4) T cells, iCD4 T cells produce effector cytokines shortly after stimulation in vitro and in vivo. iCD4 T cells express the IL-4 gene after selection in the thymus and, remarkably, Th1-differentiated iCD4 T cells produce IL-4 in addition to IFN-g. IL-4 expression in iCD4 T cells does not require Stat6 or RBP-J both of which are critical transcriptional regulators of the IL-4 gene expression. Furthermore, mTORC2 signaling that is essential for cCD4 T cells to express IL-4 is dispensable for iCD4 T cells. Oddly, however, iCD4 T cells are poor IL-17 producers compared to cCD4 T cells. RORgt expression is not induced during Th17 cell differentiation of iCD4 T cells and introduction of RORgt restores IL-17 production in iCD4 T cells. Together, iCD4 T cells possess unique characteristics and signaling pathways and molecular mechanisms for the development and functions of iCD4 T cells will be discussed.