Regulation of the immune response by nitric oxide differentially produced by T helper type 1 and T helper type 2 cells

Abstract The balance between T helper type 1 (Th1) and T helper type 2 (Th2) cells determines the outcome of many important diseases. Using cloned murine T cell lines, evidence is provided that Th 1, but not Th 2, cells can be activated by specific antigens or a T cell mitogen, concanavalin A, to produce large amounts of nitric oxide (NO). Furthermore, NO can inhibit the secretion of interleukin (IL)‐2 and interferon‐γ by Th 1 cells but has no effect on IL‐4 production by Th 2 cells. Th 1 and Th 2 cells can, thus, be distinguished by their differential production of and susceptibility to NO. NO exerts a self‐regulatory effect on Th 1 cells which are implicated in immunopathology.