NEW CELL-LINE FROM HAIRY-CELL LEUKEMIA PRODUCING INTERLEUKIN-6 AFTER EPSTEIN-BARR-VIRUS IMMORTALIZATION

A hairy-cell leukaemia (HCL) cell line, HCL-O, was established from th e peripheral blood of a 62-year-old Japanese patient with a unique var iant of HCL strongly expressing CD21, the receptor for the Epstein-Bar r virus (EBV). The HCL-O cells expressed antigens similar and dissimil ar to those expressed with the original hairy cells. The HCL-O cells w ere more mature than the original cells in their degree of B-cell diff erentiation, as indicated by a decrease of CD19 and surface immunoglob ulin (sIg) expression together with the appearance of CD38 and cytopla smic Ig (cIg). In addition, the cells expressed CD11c recognized by Le u-M5, a monoclonal antibody usually positive for HCL. Their karyotype and Ig gene rearrangement pattern were identical to those of the origi nal cells. The EBV genome was detected in the HCL-O cells but not in t he original cells. The HCL-O cells spontaneously produced a large quan tity of interleukin-6 (IL-6) in the conditioned medium, whereas IL-6 s erum level was not so high. These findings indicate that the HCL-O cel l line is derived from the leukaemic hairy cells and possibly, in vitr o EBV infection took place easily in the original hairy cells through their CD21, resulting in subsequent immortalization. IL-6 production b y HCL-O cells may be induced or enhanced by EBV, and the secreted IL-6 might play a role in their own growth or differentiation.