Analysis by SDS-polyacrylamide gel electrophoresis of an immunologically active factor of Leishmania tropica from growth media, promastigotes, and infected macrophages

The immunologically active material (EF) isolated from L. tropica growth medium by precipitation with specific antibody is the same as that previously prepared by a methanol extraction process. Further, this material has been localized in intact promastigotes, heavily infected macrophages, and amastigotes recovered from macrophage cultures. A lower molecular weight immunologically active substance was obtained from sonicated organisms, and it may be a precursor of the higher molecular weight material. Increased production of the low molecular weight substance by promastigotes exposed to macrophages supports the notion that EF may be critically involved in the infective process.