L3055 cells were incubated either alone or with CD40L, IL-4, or CD40L with IL-4 for 72 hours. During the 72-hour stimulation time, the presence of CD40 homodimers and Bcl-2 was determined at 24, 48, and 72 hours. Immunoblots were also performed after cells were incubated with the same additives for 72 hours, followed by an extended 14-day culture (including the initial 72-hour stimulation time) in normal complete medium. Cell lysates were prepared and equal amounts of total cellular protein resolved on either 10% SDS-PAGE for CD40 homodimers or 12.5% SDS-PAGE for Bcl-2. Western blots were performed and CD40 homodimers were detected used anti-CD40 MoAb G28.5. Bcl-2 was detected using anti-Bcl-2 MoAb 100. The numbers to the right of each panel group indicate the positions of molecular weight markers.