Study of rat lymphocytes by use of peanut agglutinin

Peanut agglutinin (PNA) was used to identify rat lymphocyte subpopulations. The binding of PNA on the surface of lymphocytes was assessed by fluorescence microscopy using fluoresceinated PNA. It was shown that most of the thymocytes and bone marrow cells have receptors for PNA; in spleen and lymph nodes the percentages of PNA-positive cells are around 40%. PNA was also used as a potentially mitogenic lectin. It was ascertained that lymphocytes incubated with PNA are stimulated only if they are pretreated with neuraminidase, and that only 'immunocompetent' thymocytes exhibit a very weak response. The fact that PNA slightly inhibits the [3H]uridine uptake of resting thymocytes might explain the weak mitogenicity of PNA.