Regulation of interleukin 4 production and of interleukin 4-producing cells.

Interleukin 4 (IL-4) is a cytokine with a broad range of functions on immune cells including the stimulation of IgE synthesis by B cells. IL-4 is synthesized by freshly isolated T cells following appropriate stimulation with either lectins or antibodies against selected surface antigens. IL-4 production has also been observed by freshly isolated FceR+ non-T, non-B cells. With T cell clones, IL-4 is produced by clones of the Th2 and Th0, but not of the Th1 type. The molecular basis for restricted cytokine production by such clones as well as the signals responsible for differentiation into either phenotype are only at the beginning to be understood.