Fig. 3.
CD28 IgM MoAb induces a CD28-dependent cell death (A), with DNA fragmentation (B), PARP downregulation (C), and BclXL upregulation (D). The untransfected (DC27) and CD28 stably transfected (DWT6.11) murine hybridoma T cells were treated as described in Fig 1. After an 8-hour incubation period, cells were harvested, PI stained, and analyzed by cytofluorometry (A), or DNA from DWT6.11 cells was extracted followed by electrophoretic analysis on a 1% agarose gel stained with ethidium bromide (B), or proteins were extracted followed by SDS-PAGE fractionation and immunoblotting of the same membrane with the indicated polyclonal serum, successively (C and D): lane 1, untreated cells; lane 2, anti-CD3 plus anti-CD5; lane 3, anti-CD3 plus anti-CD28 IgG; and lane 4 anti-CD28 IgM alone. Results are representative of at least three independent experiments.