Lack of lymphocyte-induced DNA fragmentation in human targets during lysis represents a species-specific difference between human and murine cells.

Significant cytotoxic lymphocyte-induced DNA fragmentation does not occur in four human target cells lysed by human natural killer lymphocytes, killer lymphocytes, or cytotoxic T lymphocytes. These results contrast with the extensive DNA fragmentation that occurs in murine target cells lysed by the analogous effector lymphocytes. Thus, DNA fragmentation, or the lack thereof, represents a species-specific difference between human and murine cells responding to lysis by cytotoxic lymphocytes. The DNase activity observed in murine cells is probably internally activated rather than delivered by the cytotoxic effector cells, since human killer lymphocytes selectively caused DNA fragmentation in murine but not in human target cells lysed by antibody-dependent cellular cytotoxicity.