Polyclonal B cell activation in hamsters infected with parasites of the genus Leishmania.

Mesocricetus auratus (golden hamsters) infected with leishmania developed characteristic B cell immune responses that depended on the infecting species of leishmania. Thus, hamsters infected with viscerotropic leishmania (Leishmania donovani) developed antileishmania antibodies and hypergammaglobulinemia due to polyclonal activation of B cells as measured by reverse hemolytic plaque assay. In contrast, dermotropic leishmanias (L. braziliensis braziliensis and L. mexicana amazonensis) stimulated antileishmania antibodies with no increase in either serum immunoglobulin concentration or in the number of antibody-forming cells per spleen. The dermotropic leishmanias were unable to stimulate polyclonal activation even in hamsters in which visceralization had occurred with high splenic parasitization. These findings suggest that species-specific leishmania antigens (or factors) might be the modulators of the altered immune response present in these diseases.