The effect of chronic daily cyclophosphamide administration on established antibody responses

Experiments are described in which the effect of prolonged daily cyclophosphamide administration on established antibody responses is assessed. The antigen used in this study was chicken red blood cells (CRBC) and IgG anti-CRBC antibody production was measured in an antibody-dependent cell-mediated cytotoxicity assay. It is concluded that prolonged administration of cyclophosphamide does cause a small fall in the level of IgG antibody production. This fall, however, is rapidly reversed when the drug is withdrawn. These data suggest that any clinical benefit of cyclophosphamide in the treatment of diseases with autoimmune phenomena may not be due to the action of the drug on antibody-producing cells or their precursors.