Lectinocytochemical specificity in human eosinophils and neutrophils: a reexamination

As with secretory granules in other cell types, many of the protein components that make up the cytoplasmic granules of human leukocytes are glycoproteins. It is not unexpected, therefore, that lectins specific for various carbohydrate moieties can be localized in these granules following appropriate protocols for specimen preparation and thin-section labeling. In this study, isolated human eosinophils and neutrophils were prepared for lectin-gold electron microscopic localization by procedures that involve no exposure to aqueous fixatives, buffers, or solvents (rapid cryofixation and molecular distillation drying), thus removing the potential problem of constituent extraction or translocation during so-called "wet chemical" processing. In contrast to other reports, data presented illustrate the specific binding of soybean agglutinin (SBA) to eosinophil granule matrices (not the crystalline cores), as well as to a population of granules in neutrophils. A similar labeling pattern for wheat germ agglutinin (WGA) was also seen, confirming the presence of N-acetyl-D-galactosamine and N-acetyl-D-glucosamine residues in eosinophil and neutrophil granule matrices. These studies emphasize the need for carefully designed specimen preparation as well as subsequent thin-section labeling procedures in lectinocytochemical studies.