Induction of oligonucleosomal DNA fragmentation. The 185-4 cells were cultured with aggregated IgG (50 μg/mL), PMA (100 ng/mL), or rIL-3 (50 U/mL) with or without staurosporine. After 24 hours, 5 × 10⁶ cells were exposed to 1 μg/mL of Jo-2 MoAb. After a 24-hour incubation, cells were collected and DNA was extracted as described in Materials and Methods. DNA (5 μg) from each sample was resolved in 1% agarose gel and visualized by staining with ethidium bromide.