A regulatory role for suppressor of cytokine signaling-1 in Th polarization in vivo

Suppressor of cytokine signaling (SOCS)-1 is an inhibitory molecule for JAK, and its deficiency in mice leads to lymphocyte-dependent multi-organ disease and perinatal death. Crossing of SOCS-1(-/-) mice on an IFN-gamma(-/-), STAT1(-/-) and STAT6(-/-) background revealed that the fatal disease of SOCS-1(-/-) mice is also dependent on IFN-gamma/STAT1 and IL-4/STAT6 signaling pathways. Since IFN-gamma and IL-4 are representative T(h)1 and T(h)2 cytokines respectively, here we investigated the role of SOCS-1 in T-h differentiation. Freshly isolated SOCS-1(-/-) CD4(+) T cells stimulated with anti-CD3 rapidly produced larger amounts of IFN-gamma and IL-4 than control cells, suggesting that these mutant T cells had already differentiated into T(h)1 and T(h)2 cells in vivo. In addition, SOCS-1(+/-) CD4(+) T cells cultured in vitro produced significantly larger amounts of IFN-gamma and IL-4 than SOCS-1(+/+) cells. Similarly, SOCS-1(+/-) CD4(+) T cells produced more IFN-gamma and IL-4 than SOCS-1(+/+) cells after infection with Listeria monocytogenes and Nippostrongyrus braziliensis respectively. Since IL-12-induced STAT4 and IL-4-induced STAT6 activation is sustained in SOCS-1(-/-) T cells, the enhanced T-h functions in SOCS-1(-/-) and SOCS-1(+/-) mice appear to be due to the enhanced effects of these cytokines. These results suggest that SOCS-1 plays a regulatory role in both T(h)1 and T(h)2 polarizations.