Monoclonal antibodies recognizing determinants specific for the promastigote stage of Leishmania mexicana

Two monoclonal antibodies (IX-IF9-D8 and IX-5H9-CI) produced to a membrane enriched fraction of Leishmania mexicana amazonensis promastigotes have been demonstrated to be specific for the promastigote (insect) form and not the amastigote (mammalian host) form of the parasite. The antigens recognized by these monoclonal antibodies are not found on amastigotes isolated from infected animals or on amastigotes isolated from a macrophage cell line J774 infected initially with promastigotes. The antigens are not re-expressed by amastigotes cultured at 34°C; however, amastigotes cultured at 24°C that have begun transformation into promastigotes do express these antigens. The level of expression of these antigens in cultures of amastigotes undergoing transformation into promastigotes, increases with time from 16 to 36 h and appears to correlate with the percentage of promastigotes. Two protein molecules with apparent molecular weights of 40 000 and 92 000 have been identified by radioimmune precipitation as associated with L. mexicana promastigote stage specific determinants.