The effect of bleomycin (Bleo) on immunocompetence in man

In animals several investigators have found that Bleo is not immunosuppressive. However, reduced thymidine incorporation has been described in phytohemagglutinin (PHA) stimulated human lymphocytes treated with Bleo. The effects were studied of Bleo on immunocompetence in 6 patients with disseminated cancer who were receiving Bleo, 15 mg/m² IM twice/wk. Humoral and cellular immunity was assessed using a panel of tests including immunoglobulin levels, isoantibody titers, recall virus antibodies, antibody production following primary vaccination with keyhole limpet hemocyanin, recall and primary delayed hypersensitivity reactions, E rosettes and lymphocyte stimulation with PHA. Patients were tested prior to treatment and after 2 and 4 wk of Bleo therapy. There was no reduction in either humoral or cellular immunocompetence in patients receiving Bleo. In vitro studies using PHA stimulated lymphocytes showed reduced thymidine incorporation at high doses of Bleo which could be corrected by removing the Bleo after 1 hr. There was no reduction in ³H leucine incorporation even at high doses of Bleo. It was concluded that Bleo has no immunosuppressing effects on either humoral or cellular immunity in man and that the reduced thymidine incorporation described in vitro was a consequence of the biochemical action of Bleo on DNA.