Interaction of wheat germ agglutinin with human peripheral blood mononuclear cells. Binding kinetics and flow microfluorometric analysis

Abstract

We have used binding experiments with radiolabeled lectin and flow microfluorometry to characterize the interaction of wheat germ agglutinin (WGA) with human peripheral blood mononuclear cell preparations. Results indicated that WGA bound to these cells in a complex fashion described by a curvilinear (upwardly concave) Scatchard plot and a nonlinear dissociation curve. Binding was rapid and reversible and was inhibited 80–90% by 0.1 M N-acetylglucosamine, a specific haptenic inhibitor of WGA binding. Approximately 1 5 of the total binding was attributable to monocytes, (but phagocytic uptake was excluded), and the remainder was due to lymphoid cell variants. Kinetics of binding were only modestly altered by formalin fixation of the cells mitigating against a role for site-site interactions in the generation of the non-linear Scatchard plot. Flow microfluorometric analysis revealed that the capability to bind WGA was a characteristic of only 35% of blood mononuclear cells and further allowed identification of a small cell subclass constituting less than 10% of the total that nonetheless accounted for fully one half of the entire WGA binding potential of these cells.