Detection of lymphocyte stimulation by flow cytometry: differences in cells from patients with and without neoplasia.

Fluorescence polarization measurements were performed to detect PHA-stimulation of peripheral lymphocytes in an early state. Single cell fluorescence was measured by flow cytometry using an epi-illumination design to avoid the influence of background fluorescence and multiscattering. By these arrangements the accuracy in the determination of P, the degree of polarization, could be improved over the usual cell suspension measurements. Fluorescence polarization measurements were performed on density specified human lymphocytes after incubation with fluorescein diacetate with and without preincubation with phytohemagglutinin (PHA). A group of healthy donors had an average polarization of P = 0.17 before and P = 0.12 after PHA-stimulation, whereas a group of patients with malignant disease showed an average polarization of P = 0.14 before and after PHA-stimulation.