Alpha-interferon activated cytotoxic lymphocytes in hairy cell leukemia patients: evaluation of cytotoxic events.

To further define the mechanisms responsible for the alpha-interferon (alpha-IFN) efficacy in the treatment of hairy cell leukemia (HCL), experiments were carried out to specify the cytotoxic events taking place following this type of therapy. Although an increased natural killer (NK) activity was demonstrable after alpha-IFN treatment, evidence has been provided that hairy cells were not specifically lysed either by fresh autologous/allogenic NK lymphocytes or by lymphokine activated killer (LAK) cells. This property could not be induced in vitro by alpha-IFN or by interleukin-2 (IL-2). Our data favour the hypothesis that the increase of NK cell activity observed following alpha-IFN therapy has not a direct antineoplastic effect but is likely to be of relevance for a non-specific enhancement of the host immune system. In alpha-IFN treated HCL this latter property may account for the better resistance to infections which usually represents the major cause of mortality in these patients.