IMMUNOELECTRON MICROSCOPIC LOCALIZATION OF GALECTIN-3, AN IGE BINDING-PROTEIN, IN HUMAN MAST-CELLS AND BASOPHILS

Galectin-3 is an endogenous soluble lectin within the family called ga lectins that bind beta-galactosides. Homologs of the protein isolated hom different sources were previously designated as IgE-binding protei n (epsilon BP), CEP35, CPB30, Mac-2, RL-29, RLL, L-29, and HL-29. All are now renamed galectin-3. This lectin is widely distributed in cells and tissues of mice, rats, dogs, hamsters, and humans. Light microsco pic immunohistochemistry and ultrastructural immunogold labeling metho ds were used to determine the distribution of galectin-3 in human mast cells of several organs, in mast cells developed in vitro from human fetal liver cells, and in human peripheral blood basophils. Immunolabe ling for the protein was observed in mast cells from all sources and i n basophils. The lectin was detected in the nucleus and/or the cytopla sm. The nuclear labeling was over heterochromatin whereas euchromatin was unlabeled. Cytoplasmic labeling was concentrated over secretory gr anules. The intensity of staining generally was greater in mast cells of skin when compared with that of mast cells in other locations and w ith that of basophils. Studies have indicated that in mast cells galec tin-3 may be involved in promoting their adhesion to basal laminae. In this study the localization of galectin-3 in the secretory granules o f human mast cells and basophils suggests that these cells may release this lectin when activated to degranulate. (C) 1995 Wiley-Liss, Inc.