The interaction of maintenance interferon with cytolytic cells in patients with multiple myeloma who responded to cytotoxic chemotherapy.

Abstract

To determine the long-term effects of maintenance interferon on CD56+ and CD3+ cell activity. Prospective phase II trial. Tertiary medical center and level 2 Veterans Administration hospital. Seven patients (age 45-74 yrs) with multiple myeloma who had reached the plateau phase from cytotoxic chemotherapy, and seven age- and sex-matched controls. All patients were given interferon-alpha 2b 3 x 10(6) U/m2 3 times/week. The CD56+, CD3+, and CD16+ counts were determined by flow cytometry in both peripheral blood and bone marrow. Natural killer (NK) cell functional activity was determined by a 51chromium release assay. Monocyte cell numbers were determined from the white blood cell count with differential. Interleukin-6 (IL-6) concentrations were determined by a commercially available enzyme-linked immunosorbent assay. During the 24-week study, the peripheral blood CD3+ and monocyte counts in patients with myeloma remained constant (p > or = 0.39) but their absolute CD56+ counts decreased significantly (p = 0.05). In peripheral blood, CD56+, CD16-, CD3- was the predominant phenotype in patients. The predominant phenotype in bone marrow was CD56+, CD16-, CD3+ at baseline but changed to CD56+, CD16-, CD3- by week 24. The cytolytic activity of NK cells significantly increased in bone marrow (p = 0.05) whereas it remained stable in the peripheral blood (p = 0.55), but only half that of the controls. Concentrations of IL-6 did not increase significantly during the study. In peripheral blood, NK cell activity remained stable in patients but was significantly lower than that in controls, probably secondary to the predominance of the CD56+, CD16-, CD3- phenotype in the patients. In contrast, NK cell activity increased significantly in bone marrow despite the predominance of the CD56+, CD16-, CD3- phenotype by week 24.