AN IMMUNOSUPPRESSIVE FACTOR IN THE SERUM OF BABOONS (PAPIO-ANUBIS) INFECTED WITH SCHISTOSOMA-MANSONI

Abstract

Serum taken from baboons infected with S. mansoni suppressed in vitro reactivity of normal baboon lymphocytes. The concanavalin A response was significantly suppressed by such serum, whereas the specific suppression of the phytohemagglutinin response was minimal. Serum from S. mansoni-infected donors depressed the mixed lymphocyte reactions to xenogeneic targets but did not affect the specific transformation of lymphocytes stimulated with a parasite Ag. Significant suppressive activity occurred in the baboon serum from 4-11 wk after the initial infection. Serum from animals with a chronic infection of 6-42 mo. did not suppress in vitro cell-mediated immunity. The suppressive factor was heat-stable, non-dialyzable and, following ultracentrifugation of the suppressive serum, was present in the high MW fraction. The immunosuppressive factors may be immune complexes which appear in the serum of the baboons following their infection with this blood parasite.