THE INTERACTION OF MAINTENANCE INTERFERON WITH CYTOLYTIC CELLS IN PATIENTS WITH MULTIPLE-MYELOMA WHO RESPONDED TO CYTOTOXIC CHEMOTHERAPY

Study Objective. To determine the long-term effects of maintenance int erferon on CD56+ and CD3+ cell activity. Design. Prospective phase II trial. Setting. Tertiary medical center and level 2 Veterans Administr ation hospital.Patients. 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. Interventions. All patients were given interferon-alpha 2b 3 x 10(6) U/m(2) 3 times/week. Measurem ents and Main Results. The CD56+, CD3+, and CD16+ counts were determin ed by flow cytometry in both peripheral blood and bone marrow Natural killer (NK) cell functional activity was determined by a (51)chromium release assay. Monocyte cell numbers were determined from the white bl ood cell count with differential. Interleukin-6 (IL-6) concentrations were determined by a commercially available enzyme-linked immunosorben t assay. During the 24-week study, the peripheral blood CD3+ and monoc yte counts in patients with myeloma remained constant (p greater than or equal to 0.39) but their absolute CD56+ counts decreased significan tly (p=0.05). In peripheral blood, CD56+, CD16-, CD3- was the predomin ant phenotype in patients. The predominant phenotype in bone marrow wa s CD56+, CD16-, CD3+ at baseline bur 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 blo od (p=0.55), but only half that of the controls. Concentrations of IL- 6 did not increase significantly during the study. Conclusion. In peri pheral blood, NK cell activity remained stable in patients but was sig nificantly lower than that in controls, probably secondary to the pred ominance of the CD56+, CD16-, CD3- phenotype in the patients. In contr ast, NK cell activity increased significantly in bone marrow despite t he predominance of the CD56+, CD16-, CD3- phenotype by week 24.