G-CSF reduces IFN-γ and IL-4 production by T cells after allogeneic stimulation by indirectly modulating monocyte function

Despite a 10-fold increase of T cell dose, the incidence and severity of acute GVHD following allogeneic transplantation of G-CSF-mobilized PBSC is not increased compared to BMT. Experimental murine studies demonstrate that G-CSF polarizes donor T cells toward a type 2 cytokine response. To determine whether G-CSF alters T cell cytokine responses, we investigated the effects of G-CSF administration on T cell proliferative and cytokine responses to alloantigen and Con A in nonadherent PBMC (NAC) and CD3(+) T cells obtained from normal individuals before and after G-CSF administration (10 mu g/kg x 4 days). Although T cell proliferative and cytokine (IFN-gamma and IL-4) responses to alloantigen stimulation and Con A were significantly reduced in post-G-CSF NAG, they were restored by the removal of non-T cells from post-G-CSF NAG. Furthermore, there was less T cell alloreactivity in MLR in the presence of autologous post-G-CSF monocytes than in the presence of pre-G-CSF monocytes. This alteration was not replicated in vitro by culturing PBMC with G-CSF. These results suggest that G-CSF administration suppresses T cell proliferative and cytokine (IFN-gamma and IL-4) responses to allogeneic stimulation by indirectly modulating monocyte function.