PROLIFERATION AND CYTOGENETIC ANALYSIS OF HAIRY-CELL LEUKEMIA UPON STIMULATION VIA THE CD40 ANTIGEN

Using the CD40 system, in vitro proliferation of hairy cell leukemia ( HCL) was examined in 43 patients. In this culture system, cells were s timulated by interleukin-4 (IL-4) and anti-CD40 monoclonal antibodies (MoAbs) that were added in soluble form or were cross-linked via their Fc part using Fc gamma RII-transfected mouse fibroblast cells. prolif eration was induced and confirmed by H-3-thymidine incorporation in 14 cases and by the presence of metaphases in 42 cases. H-3-thymidine in corporation showed a heterogeneous pattern: cross-linking of anti-CD40 gave the highest proliferation in 8 cases; in 11 cases. stimulation w ith anti-CD40 MoAbs alone, without cross-linking also resulted in prol iferation; the addition of IL-4 further enhanced H-3-thymidine incorpo ration in 5 cases, but suppressed this phenomenon in 5 other cases. Th e CD40 system proved to be very effective in obtaining cytogenetic dat a. With a success rate of 42 of 43 patients tested, we found clonal ab normalities in 8 cases (19%) and nonclonal abnormalities with involvem ent of one or two abnormal metaphases in another 7 cases. The chromoso mes most frequently involved in the abnormal karyotypes, both structur ally and numerically, were chromosomes 5, 7, and 14. By fluorescence-a ctivated cell-sorting analysis of the cultured cells, and by immunophe notypic analysis of metaphase spreads, T-cell growth could be excluded and the HCL-lineage confirmed. Stimulation via the CD40 antigen is an excellent tool for growing hairy cell leukemia cells. (C) 1994 by The American Society of Hematology.