Wheat-germ agglutinin binding in four types of mouse peritoneal macrophage. A quantitative EM-cytochemical study.

After stimulation of the mouse peritoneal cavity with newborn calf serum (NBCS), four types of monocyte and macrophage were distinguished on the basis of peroxidase (PO) patterns. These cell types showed heterogeneity in their binding of the lectin wheat-germ agglutinin (WGA). At 16 h after stimulation, monocytes and monocyte-derived macrophages (with PO activity in granules) had a high level of WGA binding; PO-negative macrophages showed moderate WGA binding, and resident macrophages (with PO activity in the RER and nuclear envelope) had low WGA binding. At later time-points after stimulation, each of these cell types lost WGA binding sites. This decrease was related to a process of differentiation and to a modulation, affected by environmental factors. The present results also indicated that PO-negative macrophages can give rise to resident macrophages. Whether these PO-negative cells are monocyte derived or originate otherwise needs further investigation. The fourth type of macrophage, the exudate-resident cell (with PO activity both in granules and in the RER and nuclear envelope), with a WGA binding pattern similar to that of monocytes and monocyte-derived macrophages, was considered not to be a resident precursor cell.