Membrane fluorescent probes for the demonstration of lymphocyte population heterogeneity. I T. and B lymphocytes of mice and rats.

Non-fixed lymphocytes of rats and mice were stained with the membrane fluorescent probe, 3-methoxybenzanthrone. The probe is capable of binding preferentially with lymphocyte membranes and fluoresces in the green spectral region. Microfluorometry of single cells showed that lymphocytes differ in all lymphoid organs and these may be a 3-10-fold variation in fluorescence intensity. Lymphocytes can be divided into two groups according to fluorescence intensity: "bright" and "dim". The proportions of "bright" and "dim" cells were determined in rats and mice for various lymphoid organs in the normal state, after thymectomy and cyclophosphamide treatment, and also after lymphocyte separation on a nylon wool column. In all cases the proportion of bright lymphocytes corresponded to the B-cell content, and the proportion of dim lymphocytes corresponded to the content of T-cells.