Prophylactic treatment with recombinant human gamma interferon (rHuIFN 0.1 mg/kg/day) had no protective effect against trophozoite-induced infections, but a strong protective effect against experimental infections with P. cynomolgi B sporozoites in M. mulatta suggesting that the interferon effect was limited to the exoerythrocytic stage of parasitic development (Maheshwari et al., 1986) thus indicating an inhibition of liver schizogony. The gene discussed is IFNG; the disease is infection.