Correlation of expression of ΔCD79b and sensitivity to anti-Fcμ–induced apoptosis of Burkitt lymphoma cell lines.

(A) Level of ΔCD79b transcript in Burkitt cell lines. To assess the level of ΔCD79b in a range of Burkitt lymphoma cell lines, RT-PCR analysis was performed using the specific primers for CD79b as detailed in Figure 1. Samples assessed were Ramos-EHRB (E), Ramos (R), Daudi (D), Raji (Rj), and Namalwa (N). For comparison, the PCR products from an example of a B-CLL (C) and an SLVL (S) are also shown. The ratios in each panel show the relative level of ΔCD79b/CD79b. (B) The levels of surface BCR on EHRB (tightly grouped dotted outline […]), Namalwa (spaced dotted outline [. . .]), Raji (solid histogram), and Daudi (light gray solid outline) cells as measured by flow cytometry. The cell lines were stained with FITC-conjugated mAb to CD79a (ZL7-4), CD79b (ZL9-1), and sIg (M15/8). (C) Induction of apoptosis with anti-Fcμ mAb. Namalwa, Daudi, and EHRB Burkitt cell lines were assessed for their sensitivity to anti-μ–induced apoptosis by exposure to 10 μg/mL anti-μ mAb for 24 hours. Apoptosis was assessed by flow cytometry using annexin V–FITC and PI. (D) Correlation of ΔCD79b expression and sensitivity to anti-Fcμ mAb. The ratio of ΔCD79b/CD79b is taken from panel A, and the sensitivity to apoptosis is taken from the same experiments as those shown in panel C.