Anti-DNA antibodies (Abs) are important in the pathogenic development of systemic autoimmune diseases, in particular systemic lupus erythematosus (SLE). These Abs have also been described in some hematologic malignancies such as chronic lymphocytic leukemia (CLL). The major known pathogenic effect of anti-DNA Abs is the induction of an inflammatory response in kidneys due to their deposition. Cross reactivity of anti-DNA Abs with several membrane antigens may induce cellular dysfunction through either alterations in some cellular pathways or penetration of the Abs into living cells. DNA-hydrolyzing activity has also been observed in the presence of some anti-DNA Abs. More recently, the description that anti-DNA specific auto-Abs can trigger apoptosis in cultured mesangial and endothelial cells provides a possible clue to understanding anti-DNA Abs' deleterious effects. To gain insights into anti-DNA Ab-induced apoptosis, the authors studied the effect of anti-DNA Abs on various tumor cell lines.