SUPPRESSION OF MURINE LYMPHOCYTE-PROLIFERATION INDUCED BY A SMALL RNAPURIFIED FROM THE TAENIA-SOLIUM METACESTODE

A substance from Taenia solium metacestodes that decreases lymphocyte proliferation induced by concanavalin A was isolated. The molecular we ight of this substance was estimated to be slightly more than 1,450 Da . Crude metacestode factor was fractionated through a Bio-gel P-6 colu mn. Peak 1 showed suppressive activity. After incubation with RNase th e substance lost its activity. Incubation of this material with trypsi n or papain increased its suppressive activity. It was stable at boili ng temperature for 10 min. The incubation of this substance with murin e macrophages had no effect on [H-3]-thymidine uptake by cocultured fr esh splenic lymphocytes stimulated with concanavalin A. Conversely, co cultures of lymphocytes pretreated with the substance and fresh spleni c lymphocytes showed a decreased incorporation of [H-3]-thymidine. The se results suggest that this substance is a RNA-peptide molecule whose RNA moiety accounts for its suppressive activity. The findings also s uggest that in vivo the factor may be a modulator of the immune respon se.