Immunoregulation in experimental filariasis. III. Demonstration and characterization of antigen-specific suppressor cells in the spleen of Brugia pahangi-infected jirds.

Antigen specific immunoregulatory phenomena in both human and experimental filariasis are correlated with the presence of circulating microfilariae. Previous studies of inbred jirds infected with Brugia pahangi have demonstrated that the onset of microfilaremia (8-10 weeks post-infection) is associated with a loss of responsiveness to parasite antigens in the spleen, but not the lymph nodes of infected animals. The present experiments defined immunoregulatory phenomena responsible for altered antigen-specific in vitro lymphocyte blastogenesis in the spleen of B. pahangi-infected jirds. Diminished splenic responsiveness to B. pahangi antigens was associated with the presence of a cell capable of suppressing the responsiveness of lymph node cells from infected jirds to parasite antigens. antigen-induced in vitro blastogenic responsiveness of spleen cells from microfilaremic , but not normal animals was restored by depletion of cells adherent to nylon wool or bearing receptors for histamine, peanut agglutinin, soybean agglutinin or jird Fc. The responsiveness of spleen cells from chronically infected (greater than or equal to 20 weeks) animals to mitogens, but not parasite antigens, was enhanced by removal of plastic-adherent cells. The results suggest the involvement of antigen-specific suppressor T cells, in the spleen of B. phangi -infected jirds which are distinct from non-specific suppressor cells previously described in this system.