T cell expansion is regulated by activated Gr-1+ splenocytes

CD4(+) T cell proliferation depends oil the balance between NO and extra-cellular superoxide (O-2(-)). By reducing NO bio-availability O-2(-) promotes splenic T cell proliferation and immune response intensity. Here, we show that spleen cells from naive mice produced neither NO nor O-2(-) during T cell activation, but Gr-1(+) splenocytes from primed mice regulated Ag-specific T cell expansion via Production of both molecules. Purified splenic Gr-1(+) cells included mostly granulocytes at various stages of maturation, its well as monocytes. Activation or recruitment of regulatory Gr-1(+) cells was dependent on immunization with CFA. Importantly, these regulatory cells were not detected in draining lymph nodes. These data suggest that innate Gr-1(+) splenic cells regulate adaptive immunity. (c) 2005 Elsevier Inc. All rights reserved.