Cyclophosphamide inhibits antibody-dependent cellular cytotoxicity (ADCC) suppression exerted by lymph node cells.

The effect of cyclophosphamide (Cy) on suppression of antibody-dependent cellular cytotoxicity (ADCC) by lymph node cells (LNC) was evaluated. The results show that the suppression of ADCC exerted by LNC was abrogated when mice had been treated with Cy. Moreover, it was shown that ADCC inhibition induced by LNC was mediated by soluble factor(s) and that treatment with a single dose of 200 mg/kg ip of Cy, significantly decreased its release. In addition, suppressor activity of normal LNC was enriched by depletion of adherent cells and was not affected by treatment with monoclonal anti-Thy 1.2 plus complement. These observations indicate that modulatory cells are nonadherent and lack characteristic T-cell markers. Thus, we conclude that this suppressor system, which normally controls ADCC activity, can be inhibited by treatment of mice with Cy and that this effect may explain the enhancement of ADCC observed in splenocytes of Cy-treated animals.