Marginal zone macrophages identified by a monoclonal antibody: characterization of immuno- and enzyme-histochemical properties and functional capacities.

In the present study, the non-lymphoid cell of the marginal zone is described: the marginal zone macrophage, identified by a monoclonal antibody, ERTR9. The characteristics of these cells were investigated by use of a two-step immunoperoxidase method (on light and ultrastructural level) in combination with enzyme-cytochemical techniques and functional tests. The marginal zone macrophage appears to be a large cell with close contacts between its cell processes and surrounding marginal zone B cells, and with a well-developed phagocytic capacity. These ERTR9-positive macrophages are capable of selective uptake and retention of i.v. injected FITC-Ficoll and are negative for Ia antigen as well as for the macrophage-related F4/80 antigen. By these characteristics, they constitute a subpopulation of non-lymphoid cells of spleen unique for the marginal zone.