Modified lymphocyte response to mitogens after intraperitoneal injection of glycopeptidolipid antigens from Mycobacterium avium complex

Abstract

Intraperitoneal injection of glycopeptidolipid (GPL) antigens from Mycobacterium avium complex serovar 4 resulted in the decreased ability of murine splenic lymphocytes to respond to nonspecific-mitogen-induced blastogenesis when exposed to concanavalin A, phytohemagglutinin, and lipopolysaccharide. Adherent cell depletion and cell mixing experiments with T lymphocytes indicated that macrophages were not a major contributor to the immunosuppression observed in this study. Enumeration of splenic lymphocytes by means of flow-cytometry with fluorescein isothiocyanate-conjugated monoclonal antibodies demonstrated that intraperitoneal injection of GPL antigens resulted in a significant decrease in Thy-1+ and Lyt-1+ cells but no change in the numbers of Lyt-2+ cells. Treatment with GPL antigens in vitro affected the ability of splenic mononuclear cells to respond optimally for concanavalin A-induced blastogenesis at 40 micrograms of GPL per 4 X 10(5) cells per 0.2 ml and lipopolysaccharide-induced blastogenesis at concentrations ranging from 5 to 40 micrograms of GPL per 4 X 10(5) cells per 0.2 ml. However, in vitro treatment with GPL antigens did not affect phytohemagglutinin-induced blastogenesis at concentrations ranging from 5 to 40 micrograms of GPL per 4 X 10(5) cells per 0.2 ml. These findings suggest that GPL antigens or their metabolites affect lymphocyte function and may be important cofactors in the overall pathogenesis of M. avium complex infections.