BAUHINIA-PURPUREA LECTIN (BPA) BINDING SPECTRA IN HYPERPLASTIC HUMAN TONSIL AND IN PERIPHERAL-BLOOD - IMMUNOHISTOCHEMICAL, IMMUNOELECTRON MICROSCOPIC, AND FLOW CYTOMETRIC ANALYSES

We studied the binding of Bauhinia purpurea lectin (BPA) to human tons ils and peripheral blood mononuclear cells by immunohistochemical, imm unoelectron microscopic, and flow cytometric techniques. The effect of several fixatives (acetone, ethanol, buffered and non-buffered formal in, B5, Bodian 11, Bouin's, Carnoy's, Zenker's, and glutaraldehyde) wa s also examined. BPA was reactive with germinal center lymphocytes, ma crophages/histiocytes, follicular dendritic cells, squamous epithelial cells, and a subset of endothelial cells. Mantle zone and paracortica l lymphocytes were nonreactive with BPA. The profile of the specific b inding characteristic of BPA lectin was found to be influenced by the fixatives. Most significantly, formalin fixation greatly reduced overa ll binding intensity, particularly making germinal center lymphocytes totally non-reactive. The reaction intensity was most prominent in fro zen sections or those fixed in Carnoy's or ethanol solution. The combi nation of heavy metal salt-containing fixatives with acetic acid usual ly did not enhance BPA binding. Glutaraldehyde solution used for immun oelectron microscopic study also preserved BPA receptors fairly well, and BPA was confined to the membrane in lymphocytes and to both the me mbrane and cytoplasm in macrophages/histiocytes and follicular dendrit ic cells. Neuraminidase treatment of tissues resulted in binding of BP A to lymphocytes that were non-reactive before treatment. Double-stain ing studies on cell suspensions from tonsils with FITC-BPA and PE-conj ugated anti-CD3 or SIg reagents revealed that 28.4% of CD3+ cells and 61.3% of SIg+ cells were BPA reactive. In PBL, 65.6% and 81.4% of CD3 and SIg+ cells, respectively, were BPA reactive. Neuraminidase treatm ent also increased the percentage of BPA-reactive lymphocytes. In conc lusion, BPA is a marker for macrophages/histiocytes and germinal cente r lymphocytes, provided that the tissues are unfixed or fixed with sui table fixatives such as ethanol or Carnoy's solution.