Cyclophosphamide blocks both antigen-specific and polyclonal immunoglobulin responses in experimental visceral leishmaniasis.

Cyclophosphamide (Cy) has been shown to modulate antibody responses in a wide range of diseases both in humans and experimental animals. Our results in Syrian hamsters infected with Leishmania donovani have shown that Cy blocks specific and polyclonal antibody production both in vivo and in vitro. This effect was achieved by weekly 100 mg/kg doses and also by a 300 mg/kg single dose. Although Cy provokes a significant decrease in B-cell numbers in infected animals, this cannot explain the suppression of antibody production since a 50% decrease in B-cells of only-infected hamsters did not reproduce the same effect in in vitro assays. Also, this suppression was not reversed either by elimination of adherent cells or by the presence of indomethacin. These data suggest that Cy affects T-cell populations involved in the control of antibody production by B-cells.