Flow cytometric analysis of lectin binding to human peripheral blood lymphocytes

The binding of fluorescein-conjugated lentil lectin and concanavalin A to the surface membrane of human peripheral blood lymphocytes was studied by flow cytometry. The lymphocytes bound 3-fold more lentil lectin molecules compared with concanavalin A molecules and lentil lectin binding approached saturation at a much lower concentration than did that of concanavalin A. Lentil lectin identified two groups of lymphocytes: a low-binding T-cell fraction and a high-binding B-cell-enriched fraction. Concanavalin A did not discriminate between these populations in unseparated lymphocytes. Competition studies indicated that lentil lectin and concanavalin A were bound to different sites on the lymphocyte surface, although about 50% of lentil lectin sites were in close proximity to concanavalin A sites.