Granulocyte–monocyte colony-stimulating factor can inhibit the intracellular replication of protozoa such as Leishmania. The justification to explore GM-CSF as immunotherapeutic agent stems from documented effects, such as monocyte mobilization, macrophage activation, the production of pro-inflammatory cytokines, and amelioration of neutropenia (63). The gene discussed is CSF2; the disease is neutropenia.