Inhibition of JNK activity induces growth arrest and apoptosis in B-lymphoma cells and can be overcome by the addition of anti-CD40 and IL-10. (A) BKS-2 murine B-lymphoma cells were cultured in 6-well plates at 1 × 10⁶ cells/well in the presence of 0 to 10 μM doses of SP600125. Two days later, cell-cycle analysis was performed on these cultured cells by PI staining as described in “Materials and methods” (top). (Bottom) Histogram of annexin V-positive cells gated on PI-negative population in the presence or absence of 10 μM SP600125. (B, top) Histogram representation of PI staining of WEHI-231 B lymphoma in the presence or absence of the JNK inhibitor. (Bottom) Histogram of annexin V-positive cells gated on PI-negative population in the presence or absence of 10 μM SP600125. In top panels, M1, M2, M3, and M4 indicate cells in sub-G₁, G₁, S, and G₂/M phases of cell cycle. In bottom panels, percentages indicate annexin V-positive cells. (C) BKS-2 B-lymphoma cells were incubated with different doses of SP600125 in the presence or absence of α-CD40 (1:1000 dilution of ascites) and IL-10 (50 U/mL), or vehicle (DMSO) alone for 2 days, and proliferation was measured as described in “Materials and methods.” Results were expressed as percentage of control response (mean ± SE of triplicate cultures) when compared with cells that were not treated with any inhibitor. Experiments were done 2 to 3 times with similar results.