Figure 1.

Ligation of CD27 induces apoptosis. (A) Ramos cells (0.5 × 10⁶/ml) were cultured with increasing concentrations (0.1, 0.2, and 0.5 × 10⁶/ml) of mock (lanes 2–4) and CD70 transfectants (lanes 5–7) for 2 days. Ramos, mock, and CD70 transfectants when cultured alone are shown (lanes 8–10). (B–E) Experiments with formaldehyde-fixed CD70 and mock transfectants, using Ramos, Raji, human CD27 transfected mouse pre-B 300 cell lines and human peripheral blood lymphocytes preactivated with phytohemagglutinin/IL-2. The effect of coligation of surface IgM (Ramos and Raji) and Ig (murine pre-B 300) using anti-human IgM and anti-mouse IgG antibodies (10 μg/ml), respectively, on CD27-induced apoptosis is also shown (B, lanes 7 and 4; C, lane 6 vs. lane 3; and D, lane 5 vs. lane 3).