LIPOPHOSPHOGLYCAN ANTIGEN SHEDDING BY LEISHMANIA-DONOVANI

The biochemical characterizations of lipophosphoglycans from various L eishmania species reported by other workers may or may not contain sev eral types of lipophosphoglycan molecules. This is the first report in which a specific lipophosphoglycan has been defined by both its antig enic and electrophoretic properties. Furthermore, a purification proce dure for this specific lipophosphoglycan is described and some biochem ical characterizations are presented. Phospholipase C and the so-calle d phosphatidylinositol-specific phospholipase C of Bacillus cereus con vert the amphipathic form of the lipophosphoglycan antigen to the hydr ophilic form. Under equivalent incubation conditions, other phospholip ases tested were not effective in conversion of the amphipathic to the hydrophilic form. Since the amphipathic form is present in conditione d media, antigen shedding cannot be explained by phospholipase C diges tion of the amphipathic form, which would result in the release of onl y the hydrophilic form into the medium. Both the pellet and the supern atant fractions of conditioned media contained both forms of the antig en and did not differ in the relative amounts of the two. This observa tion rules out membrane blebbing as the major mechanism for the releas e of the amphipathic form.