Isolation and cytochemical characterization of globule leukocytes from rat tracheal epithelium

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Abstract
Globule leukocytes, dispersed throughout the respiratory epithelium as single cells, were isolated from rat trachea and were enriched by centrifugation on a discontinuous Percoll gradient. The isolation and enrichment procedure yields a cell fraction containing 75% globule leukocytes. The cell viability, as assessed by trypan blue exclusion, was at least 98%. Cells were maintained in short-term culture without apparent loss of viability and enzyme activity. The isolated globule leukocytes seem not to express significant levels of cytotoxicity against 51Cr-labeled YAC-1 target cells. In fixed cytocentrifuge smears, globule leukocytes appear as more or less rounded to oval cells with a low nucleo-cytoplasmic ratio and with a mostly eccentrically located nucleus. Characteristic intracytoplasmic granules are stained with toluidine blue, alcian blue, and May-Grünwald-Giemsa stains. The applied cytochemical methods demonstrate that tracheal globule leukocytes are stained for alpha naphthyl acetate esterase and naphthol-AS-D-chloroacetate esterase, but not for alpha naphthyl butyrate esterase, N-acetyl-DL-phenylalanine-B-naphthyl esterase, and endogenous peroxidase. Isolated rat peritoneal cells were used as positive control cells for the cytochemical reactions. The obtained cytochemical profile of tracheal globule leukocytes is compared to the known cytochemical profile of intestinal globule leukocytes and large granular lymphocytes. The cytochemical dissimilarities between tracheal and intestinal globule leukocytes may suggst that both kinds of globule leukocytes represent a different form of the same cell type or even different cell types. The cytochemical pattern of tracheal globule leukocytes is closely related to that of large granular lymphocytes, which have been postulated as a possible source for globule leukocytes.