Synergism of IL3 together with GMCSF causes a rapid rise in neutrophils due to GMCSF and a slower rise in platelets due to IL3 which has strong stimulated effect on hematopoietic cells.The analog of GMCSF/IL3 is PIXY321. Results indicate that PIXY321 can stimulate multilineage hematopoiesis in vivo and enhance neutrophil and platelet recovery following chemotherapy and bone marrow transplantation (BMT). These results suggest that PIXY321 elicits the biological effects of both its component cytokines and represents a novel means of delivering two independent but interactive cytokines in combination Synonyms: PIXY321, GMCSF/ IL3.