Proliferative response of purified allogeneic CD4⁺ and/or CD8⁺ T cells as well as PBMCs not further purified to γ-irradiated native and CD40-stimulated B-CLL cells. Different CD4/CD8 ratios were tested. [³H] Thymidine incorporation was assessed for the last 12 hours of a 3-day culture and determined in cpm ± SD of triplicate determinations. The results shown are from one experiment and are representative for three independent experiments.