Delayed hypersensitivity granuloma formation and modulation around Schistosoma mansoni eggs in vitro. II. Regulatory...

Schistosoma mansoni granuloma modulation was first described in an in vivo murine model of schistosomiasis and was characterized as a diminished cellular responsiveness to newly formed eggs in chronic infections. This phenomenon of modulation was studied using an in vitro model of granuloma formation. Negative selection procedures using anti-Lyt-1.2, 2.2, and Qa-1 sera and complement on spleen cell populations from normal or S. mansoni-infected C57BL/6 or (C57BL/6 X A/J)F1 mice were examined for their effect on in vitro granuloma formation or modulation. These data suggest that there is a Lyt-1+2-, Qa-1+ T cell present in chronically infected spleen cells that is capable of inducing feedback suppression. In addition, selective removal of a population of Lyt-1-2+ T cells from chronically infected spleen cells augmented the ability of that population to form granulomas in vitro. The selective removal of Lyt-1+2- cells ablated the ability of chronically infected spleen cells to form in vitro granulomas. Granuloma formation is primarily dependent on a population of Lyt-1+, Qa-1+ cells, and modulation is dependent on 2 populations, 1 acting directly (Lyt-1-2+) and the other through a (Lyt-1+2-, Qa-1+) feedback mechanism of suppression.