Its ligand cytokine GM-CSF appears to exert pleiotropic effects in the intestine: although GM-CSF is generally accepted as a pro-inflammatory cytokine contributing to colitis, treatment with a recombinant human GM-CSF agent, sargramostim, has shown some benefit in Crohn’s disease patients.(Dieckgraefe and Korzenik, 2002; Korzenik et al., 2005; Valentine et al., 2009) This inconsistency raised the possibility that the functional status of the receptor molecules might play a role in the overall effect of GM-CSF stimulation. The gene discussed is CSF2; the disease is colitis.