Suppressor cells in experimental trypanosomiasis

Abstract

HUMAN and experimental forms of African trypanosomiasis are characterised by a profound suppression of immunological responsiveness. Suppression of both humoral and cell-mediated responses has been observed. Trypanosoma gambiense infections in man reduce antibody responses to Salmonella typhi (H antigen) and skin reactivity to purified protein derivative, Candida and dinitrochlorobenzene¹. T. brucei infections in mice cause marked suppression of antibody² and splenic plaque-forming cell^3,4 responses to sheep red blood cells (SRBC), and in rabbits suppress the development of experimental allergic neuritis⁵. The mechanism underlying this inhibition of immunocompetent cell function has not been elucidated. We have examined the DNA synthetic responses of spleen cells from T. brucei-infected mice to concanavalin A (con A) and phytohaemagglutinin (PHA) (both T-cell mitogens), Escherichia coli lipopolysaccharide (LPS, a B-cell mitogen) and allogeneic cells, and the ability of these cells to influence the responses of normal cells. We present evidence suggesting that suppressor cells^6,7 are involved in the immunological hyporesponsiveness observed in this disease.