Distribution of lectin receptors in the human hyperplastic tonsil: histochemical and flow cytometric analyses

The distribution of lectin receptors in the human tonsil was studied using 16 biotinylated lectins. The avidin-biotin-peroxidase complex (ABC) method was used on frozen and paraffin-embedded tissue sections. Cell suspensions were also analysed by dual flow cytometry using respective fluorescein isothiocyanate-conjugated lectins and phycoerythrin-labeled anti-CD3 and anti-human immunoglobulin. Frozen sections fixed with acetone and paraffin-embedded materials fixed in three solutions were compared for lectin affinity; ethanol-fixed sections gave best results followed by frozen and buffered formalin-fixed ones, then nonbuffered formalin. Con-A, RCA-1, LcH, WGA, MPA, PHA, PSA, PNA, SJA and GSA-1 reacted with all tissue components of the tonsil in immunohistochemical studies, but binding intensity was fixative dependent. Binding of Lotus and BPA to lymphocytes was limited to germinal center lymphocytes. Other tissue components were also reactive but staining intensity was weaker in Lotus compared with BPA. SBA and DBA did not react with lymphocytes, but reacted with macrophages/histiocytes, vascular endothelia, and epithelial cells. LBA and LPA were constantly negative with all tissue components irrespective of fixatives. Flow cytometric analyses showed that all but three (DBA, LBA and LPA) partially or totally stained lymphocyte surfaces. Lotus receptors were expressed exclusively on B-lymphocytes.