BL cell lines were incubated either alone or with CD40L, IL-4, or CD40L with IL-4 for 72 hours. Cell lysates were prepared at either 5 or 10 days (including the initial 72-hour stimulation time), and equal amounts of total cellular protein was resolved on 10% SDS-PAGE. Western blotting was performed to determine the presence of CD40 homodimers using anti-CD40 MoAb G28.5. In addition, the same lysates were resolved on 12.5% SDS-PAGE, and Western blotting was performed to detect the presence of Bcl-2 using anti–Bcl-2 MoAb 100. The numbers to the right of each panel set indicate the positions of molecular weight markers.