Fig. (2) IL4 and CD40 co-stimulation induced long-term proliferation of DLBCL B cells in vitro from DLBCL patients. Of the ten DLBCL cases analyzed, tumor cells from four patients showed continuous proliferation for more than two months, and two cell lines (GDLB-GCB1 and GDLB-GCB2) were established from these cells (a, b). These cell lines could proliferate for more than three months and could be restored after cryopreservation. The doubling time of the established cell lines of GDLB-GCB1 (from the UPN1 patient) and GDLB-GCB2 (from the UPN2 patient) was 2.9 and 1.7 days, respectively. Abbreviation: IL-4, interleukin-4; CD40L, CD40 ligand; DLBCL, diffuse large B cell lymphoma, UPN, unique patient number.