Histochemical studies on lectin binding in reactive lymphoid tissues

Using the avidin-biotin-labeled peroxidase complex (ABC) method, the staining reaction of a panel of 12 biotin-labeled lectins was studied in formalin-fixed, paraffin-embedded reactive lymph nodes and tonsils. Varying degrees of lectin binding were observed in lymphoid cells and macrophage-histiocytes with Concanavalin ensiformis (Con A), Lens culinaris (LCA), Phaseolus vulgaris (PHA), Pisum sativum (PSA), Ricinus communis (RCA), and Triticum vulgaris (WGA) agglutinins, but no evidence of binding was observed with Dolichos biflorus (DBA), Bandieraea simplicifolia (BSA), Arachis Hypogaea (PNA), Glycine soja (SBA), Sophora japonica (SJA), and Ulex europaeus (UEA) agglutinins. Three major patterns of binding were seen: the reaction products occurred along the plasma membranes (membranous), were confined to one pole of the cell membrane (cap-like), or were present diffusely in cytoplasm (cytoplasmic). The cells showing membranous and cap-like staining patterns corresponded to the lymphoid cells, as did the cytoplasmic to plasma cell and macrophage-histiocytes. Cap-like staining was observed on the lymphocytes at B and T cell areas with all 6 lectins. Thus, the presence of cap-like staining may not be useful for discrimination between B and T cells. Membranous staining, in contrast, was limited to lymphocytes of follicles (B cells) with PSA and LCA, and to germinal center cells with PHA. WGA, Con A, and RCA also reacted with the membrane of T-cell. The cytoplasmic staining reaction of macrophage-histiocytes varied markedly from one lectin to the other. Our study indicates that the carbohydrate moiety of the cells retains their binding sites for lectins through routine processing, providing a means of valid retrospective studies. Furthermore, these observations suggest that each letin, despite its identical inhibitory sugar, should be tested for its unique reaction pattern, which is not predictable from the data derived from cell suspension studies.