Proliferation of precursor B-lineage acute lymphoblastic leukaemia by activating the CD40 antigen

No reliable culture system exists for B-lineage acute lymphoblastic leukaemia (ALL). Recently we found that many different mature B-cell malignancies proliferate upon stimulation via the CD40 antigen, and this led us to investigate whether a similar CD40 activation on ALL cells could also induce proliferation. First, we measured CD40 expression in 21 ALL cases; all were CD40⁺, although mostly weak. Next, we triggered the CD40 antigen by anti-CD40 antibodies and by a CD40 ligand-expressing cell line. In addition, we measured the influence of IL-3, IL-4 and IL-7 with and without these stimuli.  In 8/10 cases proliferation, measured by ³H-thymidine incorporation, could be induced after CD40 crosslinking, especially in the presence of IL-3. Stimulation via the CD40 ligand was more successful than using crosslinked anti-CD40 antibodies. IL-4 inhibited the spontaneous proliferation found in three cases, but stimulated proliferation after CD40 crosslinking. IL-7 did not contribute to proliferation. Morphology, immunophenotyping and surface marker analysis, combined with DNA flow cytometry confirmed that the proliferation found could be ascribed to the ALL cells.  In conclusion, B-lineage ALL cases are CD40⁺, and many can be cultured using CD40 stimulation and IL-3.