Fig 6.

Schematic representation of the mechanism by which low concentrations of NO selectively enhance type 1 T cell differentiation. Type 1 cells differentiate from Tp cells through TCR activation by antigen (peptide) presented by the MHC of the APC (e.g., dendritic cells and macrophages) in the presence of IL-12. NO produced by the APC in response to infection or present exogenously in the microenvironment can up-regulate the levels of cGMP in the Tp cells by activating sGC. cGMP, in turn, selectively enhances the expression of IL-12Rβ2. This then increases the response of Tp cells to IL-12 and, hence, preferentially promotes the differentiation of type 1 T cells.