Figure 3.
BAFF and APRIL protect HMCLs from IL-6 deprivation–induced apoptosis. (A) XG-13, XG-14, and XG-20 were IL-6 starved for 3 hours and cultured without cytokine, or in the presence of BAFF (200 ng/mL), APRIL (200 ng/mL), or IL-6 (3 ng/mL). Results are the mean values plus or minus standard deviation (SD) of the tritiated thymidine incorporation determined on sextuplet culture wells and are expressed as the percentage of the proliferation obtained with IL-6. Results are those of one experiment representative of 5. *Mean value is significantly different from that obtained without adding cytokine using a Student t test (P ≤ .05). (B) XG-13 and XG-14 HMCLs were cultured at 105 cells/mL without cytokine or in the presence of IL-6 (3 ng/mL), BAFF (200 ng/mL), or APRIL (200 ng/mL). Cells were recovered after 3 days of culture and apoptotic cells were detected by annexin V staining. Results are those of one experiment representative of 5. The percentage of apoptotic cells is indicated in each panel. (C) XG-13 cells were IL-6 starved for 3 hours and cultured without cytokine, or in the presence of IL-6 (3 ng/mL), BAFF (200 ng/mL), or APRIL (200 ng/mL). When indicated, TACI-Fc (10 μg/mL) or anti–IL-6 MoAb (10 μg/mL) was added. Results are the mean values plus or minus SD of the tritiated thymidine incorporation determined on sextuplet culture wells and are expressed as the percentage of the proliferation obtained with IL-6. Results are for one experiment representative of 3. * Mean value is statistically significantly different from that obtained with either BAFF, APRIL, or IL-6 using a Student t test (P ≤ .05). (D) XG-13 and XG-14 cells were cultured, respectively, at 2.5 × 105 and at 1.5 × 105 cells/mL without cytokine or in the presence of IL-6 (3 ng/mL), BAFF (200 ng/mL), or APRIL (200 ng/mL). Every 3 or 4 days, cells were counted and diluted with fresh culture medium containing the initial cytokine concentration. Results are the cumulative cell numbers obtained within 20 days of culture and are those of one experiment representative of 2.