Heterogeneity of concanavalin A binding by mouse peritoneal macrophages

The binding of the lectin concanavalin A (Con A) to the cell surface of monocytes and macrophages collected from the stimulated peritoneal cavity of mice was investigated electron microscopically with horseradish peroxidase-gold as an indirect marker. Individual cells were identified by the cytochemical localization of peroxidatic (PO) activity. In monocytes and monocyte-derived macrophages with PO activity in cytoplasmic granules, the degree of Con A binding was lower than in resident macrophages with PO activity in the rough endoplasmic reticulum and nuclear envelope. An even higher degree of Con A labelling was found on the surface of cells devoid of PO activity. Since the above-mentioned cell populations show a different degree of lectin binding, it is suggested that lectin labelling methods might offer a new tool for quantitative investigation of the differentiation of monocytes and resident macrophages.