Splenic NK1.1-negative, TCR alpha beta intermediate CD4(+) T cells exist in naive NK1.1 allelic positive and negative mice, with the capacity to rapidly secrete large amounts of IL-4 and IFN-gamma upon primary TCR stimulation

Splenic NK1.1(+)CD4(+) T cells that express intermediate levels of TCR alph a beta molecules (TCRint) and the DX5 Ag (believed to identify an equivalen t population in NK1.1 allelic negative mice possess the ability to rapidly produce high quantities of immunomodulatory cytokines, notably IL-4 and IFN -gamma, upon primary TCR activation in vivo. Indeed, only T cells expressin g the NK1.1 Ag appear to be capable of this function. In this study, we dem onstrate that splenic NK1.1-negative TCR(int)CD4(+) T cells, identified on the basis of Fc gamma R expression, exist in naive Nk1.1 allelic positive ( C57BL/6) and negative (C3H/HeN) mice with the capacity to produce large amo unts of IL-4 and IFN-gamma after only 8 h of primary CD3 stimulation in vit ro. Furthermore, a comparison of the amounts of early cytokines produced by Fc gamma R(+)CD4(+)TCR(int)) T cells with NK1.1(+)CD4(+) or DX5(+)CD4(+)TC R(int) T cells, simultaneously isolated from C57BL/6 or C3H/HeN mice, revea led strain and population differences, Thus, Fc gamma R defines another sub population of splenic CD4(+)TCR(int) cells that can rapidly produce large c oncentrations of immunomodulatory cytokines, suggesting that CD4(+)TCR(int) T cells themselves mag represent a unique family of immunoregulatory CD4() T cells whose members include Fc gamma R(+)CD4(+) and NK1.1/DX5(+)CD4(+) T cells.