Spontaneous apoptosis in NS-1 myeloma cultures: effects of cell density, conditioned medium and acid pH.

Apoptosis is a form of cell death which plays an important role in many biological processes including the regulation of B and T lymphocyte functions. We report here the spontaneous development of extensive apoptosis in cultures of the NS-1 mouse myeloma cell line following overgrowth. The apoptosis was identified by both its ultrastructural features and its DNA fragmentation pattern. High cell density and conditioned medium, but not acid pH, were found to be major inducers of apoptosis in this experimental system.