Relationship between delayed hypersensitivity response and acquired cell-mediated immunity in C57BL/6J mice infected with Leishmania donovani.

The relationship between the development of acquired cell-mediated immunity and the concomitant level of specific delayed hypersensitivity (DH) in C57BL/6J mice infected with the intracellular protozoan parasite Leishmania donovani was studied. It was determined that the intradermal injection of Leishmania antigen (heat- or phenol-killed flagellated forms of L. donovani) could elicit a DH response as early as day 10 and as late as day 120 postinfection in mice infected by the intravenous route. Dose-response studies showed that there is an inverse relationship between the size of the infecting dose of parasites and the magnitude of the DH response. Thus, increasing the degree of infection depressed the DH response. This depression, however, could be abrogated by treatment of mice with cyclophosphamide (201 mg/kg) before intradermal injection of antigen.