Eosinophils activation in post-autologous bone marrow transplanted patients treated with subcutaneous interleukin-2 and interferon-alpha 2A immunotherapy.

We evaluated eosinophils morphology, physical properties and antileukemic activity in autologous bone marrow transplanted (ABMT) patients treated with subcutaneous recombinant interleukin 2 (rIL-2) and recombinant human interferon alpha 2a (IFN alpha) given as outpatient immunotherapy. All patients receiving rIL-2/IFN alpha therapy developed peripheral blood eosinophilia of 20-40% peaking at 2-4 weeks of therapy. While on rIL-2/IFN alpha therapy the eosinophils became hypodense and hypersegmented. The antibody dependent cell-mediated cytotoxic activity (ADCC) of the eosinophils against the human B-cell lymphoma cell line (Raji) was depressed post-ABMT. Prolonged (28 days) in vivo rIL-2/IFN alpha immunotherapy enhanced ADCC activity of the eosinophils and brought them to normal levels. Similarly, rIL-2/IFN alpha immunotherapy enhanced the depressed cytotoxic activity of neutrophils post-ABMT to normal levels. Thus, eosinophils and neutrophils from rIL-2/IFN alpha-treated ABMT recipients may be targeted toward tumor cells by antibody, and express tumoricidal activity. No effect of rIL-2/IFN alpha was observed on monocyte-dependent ADCC activity which remained normal post-ABMT. We conclude that in addition to their effect on lymphocytes, cytokine-mediated immunotherapy consisting of subcutaneous low doses of riL-2 and IFN alpha may mediate their therapeutic effects in cancer therapy by increasing the number of eosinophils and enhancing the antitumor activity of eosinophils and neutrophils, provided that tumor-specific or tumor-associated antibodies are present.