Measurement of cytoplasmic viscosity by fluorescence polarization in phytohemagglutinin-stimulated and unstimulated human peripheral lymphocytes.

We have developed an improved technique of fluorescence polarization for measurement of the cytoplasmic viscosity of human peripheral lymphocytes. When measured using this improved method, the mean value of fluorescence polarization in lymphocytes from 20 healthy donors was 0.190 +/- 0.005. The mean value of fluorescence polarization as percent of control after stimulation of lymphocytes with phytohemagglutinin (PHA) was 83.6 +/- 3.8%. We discuss here optimal conditions for PHA stimulation of lymphocytes.