The following abstract presents results of a study conducted by a contract laboratory for the National Toxicology Program. The findings have not been peer reviewed and were not evaluated in accordance with the levels of evidence criteria established by NTP in March 2009. The findings and conclusions for this study should not be construed to represent the views of the NTP or the U.S. Government.
The sulfone, dapsone, is an anti-leprosy drug that is currently being used to treat Pneumocystis carinii pneumonia in AIDS patients. The present study was conducted to investigate the immunotoxicological potential of this drug and attempt to reproduce the immunotoxicological effects seen in a previous study. Female C57BL/6 mice were treated orally with dapsone daily for 30 days. The dose-levels used were 3.4, 13.5, and 54.0 mg/kg/day. Treatment at the high dose level resulted in erythropenia. Necropsy showed enlarged, dark red spleens. This effect on peripheral blood hematology was not associated with any changes in bone marrow cell number, or the ability of the bone marrow to form erythroid or myeloid cell colonies. There appeared to be a preferential effect on humoralmediated immunity. At the high dose level, B cell percentages were decreased, and the spleen cell proliferative response to lipopolysaccharide was increased. These effects on B cell function were concurrent with no effects seen on T cell function as measured by the spleen cell proliferative response to concanavalin A and phytohernagglutinin and the mixed-lymphocyte response. In addition, no effects were seen on natural killer cell activities. Effects on immune function were seen at the 54.0 mg/kg/day dose level, and a no-effect level was seen at the 13.5 mg/kg/day dose level.