Isolation and surface labeling of murine polymorphonuclear neutrophils

Methods for the induction of an exudate of polymorphonuclear neutrophilic leukocytes (PMN) in the peritoneal cavity of C57BL, BALB/c, SJL and CBA mice were analysed. Peritoneal exudates in male mice were highly enriched for PMN (80-90%) three hours after a single injection of calcium caseinate whereas eosinophils comprised less than 1% of the exudate population. Female mice were a less satisfactory source of PMN because the proportion of eosinophilis in the exudate was variable. Purification of PMN from peritoneal exudate cells was performed on the basis of light scattering using a Becton-Dickinson cell sorter or by density gradient centrifugation with graded polyvinylpyrrolidone-coated silica particles (Percoll). Both techniques yielded approximately 97% pure PMN preparations. Electrophoretic analysis of the PMN proteins revealed an abundance of lactoferrin and actin, but several other proteins were also present in high concentrations. Proteolytic degradation of several high molecular weight proteins (greater than 90,000) was prevented by the addition of phenylmethylsulphonyl fluoride (PMSF) and ethylene diamine tetracetic acid (EDTA). Surface iodination, using diphenyl, tetrachloroglycouril (IODO-DEN), indicated that there were six tyrosine-containing proteins present on the external cell membrane. The apparent molecular weights of these surface proteins ranged from 185,000 to 90,000 and the major 125I-labeled protein had an apparent molecular weight of 90,000. Neither actin nor lactoferrin was labeled with 125I unless cell viability was lost during the iodination procedure. Standard conditions for labeling the cell surface only, required low iodide and IODO-GEN concentrations. Biosynthetic labeling of PMN using S-methionine increased the sensitivity of detection for most of the proteins, but some of the granule storage proteins (such as lactoferrin) were not effectively labeled within three hours.