Regulation of immune responses by T cells with different cytokine secretion phenotypes: role of a new cytokine, cytokine synthesis inhibitory factor (IL10).

Subsets of T cells, defined by the patterns of cytokines that they secrete, show important functional differences, and appear to be at least partly responsible for the different immune responses induced by various pathogens. Two very distinct subsets, TH1 and TH2, are mutually inhibitory, and a newly discovered cytokine, IL10, is one of the mediators of this cross-regulation. IL10 inhibits the synthesis of cytokines by TH1 cells but not TH2 cells. Since TH2 cells produce IL4 and IL5, which lead to some of the major manifestations of allergy, it is likely that IL10 production biases an immune response towards allergy.