Lymphocyte activation and the increase of nuclear birefringence.

Nuclear birefringence of neutral red or rivanol stained cell suspensions from rat spleen has been investigated. Polyclonal or monoclonal mitogens produced an increased birefringence of the nucleus following 30 min in vitro stimulation at 37 degrees C. The nuclear birefringence increased by 62.2% [p less than 0.001], when the cells were incubated in the supernatants of a previously phytohemaglutinin stimulated culture. Amantadine, a potent phytohemagglutinin inhibitor, was unable to prevent the effect of the supernatant, but heating for 1 h at 56 degrees C destroyed its activity. The results suggest that increase in nuclear birefringence is mediated by a soluble factor which is released in the course of lymphocyte activation. The nuclear birefringence of surviving cells from human spleens obtained within 6 to 24 h post mortem increases after in vitro stimulation.