Antibody-induced movement of protozoan surface membrane antigens

Direct and indirect immunofluorescence techniques were used to study the effects of host antibodies on surface membrane antigens of viable Leishmania parasites in vitro. Antisera to L. enriettii and L. tropica caused surface membrane antigens of these parasites to aggregate, move toward the poles of the parasite, and to eventually disappear. This sequence did not occur at low temperature or in the presence of some metabolic inhibitors. Antigen subsequently reappeared on the parasite membrane. These phenomena appear to be similar to those described in mammalian cells. Antibodies may therefore effect an alteration in the surface membrane structure of living protozoan parasites.