A new rapid method for the in vitro demonstration of tonsillar lymphocyte activation.

A simple method is presented suitable for the demonstration of the initial stage of lymphocyte activation. The method is based on the evaluation of the intranuclear birefringence of lymphocytes. With this technique, the activation of the cells is detectable after 30 minutes' in vitro activation. Tonsillar lymphocyte activation was demonstrated after phytohemagglutinin, antigen, or anti-mu antibody stimulation. This activation causes an increase in the intranuclear birefringence. A small group of rabbit tonsillar lymphocytes showed an increased birefringence without in vitro stimulation, thus indicating a continuous in vivo activation of the tonsils.