In vitro and in vivo effector function of rat IgG2a monoclonal anti-S. mansoni antibodies.

Rat IgG2a monoclonal antibodies have been produced after fusion of spleen cells from LOU/C rats infected with S. mansoni for 5 wk and IR983F nonsecreting rat myeloma cells. The cell supernatants of one particular IgG2a-producing clone (IPL Sm1) as well as ascitic fluids induced by this clone revealed anti-S. mansoni activity detected by immunofluorescence on schistosoma sections. In vitro studies of the effector function of such antibodies revealed that the rat IgG2a monoclonal antibodies mediated high levels of rat eosinophil-dependent cytotoxic effect against S. mansoni schistosomula, similar to that obtained with 5-week infected rat serum. Passive transfer experiments carried out with IPL Sm1 ascitic fluid showed a significant level of passive protection against a challenge infection. These results indicate a possible use of the monoclonal antibodies in analyzing in vivo functions of IgG2a antibodies, as well as in isolating potentially protective target antigens.