RECOMBINANT INTERLEUKIN-2 INFUSIONS AND DECREASED IGG2 SUBCLASS CONCENTRATIONS

The administration of low doses of recombinant interleukin-2 (rIL-2) i n vivo to patients with malignant neoplasms has been demonstrated to s electively increase the number of circulating natural killer (NK) cell s in these patients. Recent evidence from SCID mouse models suggests t hat IgG subclass levels can be influenced by the presence and activity of NK cells. Therefore, we sought to examine the effect of rIL-2 infu sions on human serum IgG subclass concentrations. We determined serum IgG subclass concentrations in 27 cancer patients receiving low-dose r IL-2 by daily continuous intravenous infusion. Eleven of these patient s had active, metastatic, nonhematologic tumors; 16 patients had recei ved IL-2 when they were in a minimal residual disease state after auto logous or allogeneic bone marrow transplantation. Samples obtained bef ore beginning IL-2 therapy and 8 to 10 weeks into therapy were tested. Treatment with IL-2 resulted in an increase in the percentage of CD56 + NK cells from 18% to 54% (P = .0001). A significant decrease in geom etric mean lgG2 concentration from 2,017 mu g/mL to 1,655 mu g/mL was noted over this time interval (P = .03). Furthermore, the geometric me an lgG2 concentration after treatment was significantly lower than tha t of healthy controls (P = .026). In contrast, no significant changes in serum IgG1, IgG3, or IgG4 were noted during r-IL2 infusions. Our da ta suggest that rIL-2 treatment selectively decreases serum lgG2 conce ntrations. We speculate that increased NK cells mediate downregulation of human serum IgG2. (C) 1995 by The American Society of Hematology.