Effect of granulocyte colony-stimulating factor (G-CSF) on allogeneic immune responses

The administration of recombinant human granulocyte colony- stimulating factor (rhG-CSF) increased weight and cellularity of the spleen, leukocyte and granulocyte count of the peripheral blood in a dose- and duration-dependent fashion in mice. When spleen cells as well as serum from mice treated with intraperitoneal injection of 200μg/kg of rhG-CSF daily for 7 days were added to an allogeneic mixed lymphocyte reaction (MLR) culture, MLR was significantly suppressed nonspecifically and in a dose-dependent fashion. MLR was also suppressed by adding supernatant of spleen cells using transwells, indicating that suppression was mediated by soluble factor (s) secreted from the spleen cells. The producer cells of the inhibiting factor were found in more mature granulocytes with a high density in the spleen. These results suggested that the proliferated granulocytes induced by G-CSF produced and released factor (s) that suppress allogeneic immune responses.