CHARACTERIZATION OF B-CELL LINES ESTABLISHED FROM 2 X-LINKED SEVERE COMBINED IMMUNODEFICIENCY PATIENTS - INTERLEUKIN-15 BINDS TO THE B-CELLS BUT IS NOT INTERNALIZED EFFICIENTLY

X-linked severe combined immunodeficiency (XSCID) is characterized by absent or profoundly reduced numbers of T cells and normal numbers of B cells in the circulation. Affected patients have mutations of the in terleukin-2 (IL-2) receptor gamma chain gene. Using Epstein-Barr virus -transformed B-lymphoblastoid cell lines (B-LCLs) established from two unrelated XSCID patients, we could show that neither expressed the IL -2 receptor gamma chain on the cell surface. A novel cytokine IL-15, w hich has biologic activities similar to those of IL-2, could bind to t he XSCID B-LCLs in the absence of the gamma chain, although both the b eta and gamma chains of the human IL-2 receptor were previously shown to be required for IL-15 binding by transfected COS cells. Furthermore , a significant reduction and delay of IL-15 internalization by B lymp hoblasts from XSCID patients was observed when compared with that of n ormal control B-LCLs. These results show the existence of a novel IL-1 5-specific receptor component that contributes to IL-15 binding but is insufficient for IL-15 internalization in the absence of the IL-2 rec eptor gamma chain. (C) 1995 by The American Society of Hematology.