Immunomodulatory activity of human leukocyte interferon in cancer patients: results obtained during pulse therapy schedule.

We evaluated and previously reported the efficacy of alpha-interferon (alpha-IFN) in 84 cancer patients (19). IFN was administered in a pulse fashion given for 3 consecutive days every 4 weeks. We also evaluated the immunomodulatory effect of IFN which constitutes the basis for the current report. Before, during and after courses of IFN treatment, the immune status of the patients was assessed by: (i) circulating immune complexes, (ii) change in lymphocyte type including (a) natural killer (NK) cells, (b) T-cell subsets (suppressor, helper) and (c) HLA-Dr antigen positivity, (iii) myelopoietic differentiation, (iv) macrophage-dependent tumor cytotoxicity with measurements of macrophage-derived growth factor (MDGF), (v) granulocyte functions, (vi) antibody formation against IFN, and (vii) antiproliferative activity of IFN. In addition, LDH, beta-2 microglobulin, and CEA as tumor markers were obtained. High serum or plasma IFN levels were associated with increased activity of T suppressor cells, increased HLA-Dr antigen, and increased NK activity. The increase of these three parameters was directly related to tumor response. In vitro inhibition of tumor cells in tissue culture by IFN culture was predictive of objective tumor response in those patients whose tumor cells were tested. In addition, IFN induced release of MDGF by monocytes. It is apparent that in addition to direct antitumor effect, IFN has multiple modulatory effects on the immune system in man that may aid in tumor control when given in a pulse schedule.