Cepaea hortensis agglutinin-I, specific for O-glycosidically linked sialic acids, selectively labels endothelial cells of distinct vascular beds

The lectin Cepaea hortensis agglutinin-I (CHA-I) binds to O-glycosidically linked sialic acids with previously characterized specificity. Employing histochemistry, we demonstrate that CHA-I is a useful probe for detecting sialic acids in formalin-fixed human tissues in a specific manner. It stains the endothelium of arteries and veins in all tissues examined, and labels the capillaries in distinct vascular beds including the brain, colon, thyroid, pituitary, and adrenal. By contrast, the endothelial sinusoids in the liver, spleen, and bone marrow remained unstained. The staining pattern of CHA-I overlaps with the distribution of the sialomucin and L-selectin ligand podocalyxin, which includes positivity of podocytes and interstitial but not glomerular capillaries. CHA-I-positive epithelial structures were found in the lung, liver and kidney. Colon carcinoma cells were labelled with CHA-I but not haemangiosarcomas. In summary, CHA-I is a useful tool for detecting O-glycosidically linked sialic acids in formalin-fixed tissues, and a potentially powerful tool for the isolation and characterization of unknown sialomucins in normal and eventually in diseased tissues.