Characterization of monoclonal antibodies specific for monocytes, macrophages and granulocytes from porcine peripheral blood and mucosal tissues.

A panel of four monoclonal antibodies produced in our laboratory, MIL1, MIL2, MIL3, MIL4, and the type-specific monocyte/granulocyte marker 74-22-15 were used to isolate and to discriminate between monocytes, macrophages and granulocytes derived from porcine peripheral blood, lung and gut lamina propria. Two-colour flow cytometry and cell sorting showed that while no monoclonal antibody was specific for just a single cell population, each cell type had a unique and characteristic combination of surface antigens. These differences could be used to identify and purify monocytes, macrophages, neutrophils, eosinophils and basophils from the three different sites. The study also demonstrated similarities and differences within cell types from the same site and from different sites: polymorphonuclear neutrophils (PMN) from peripheral blood were subdivided into two subpopulations by the presence or absence of the surface antigen recognized by MIL4, while PMN from alveolar lavage did not express this antigen. Peripheral blood eosinophils were also divided into subpopulations by the presence or absence of the same surface antigen. Lamina propria eosinophils strongly expressed the MIL4 marker and differed morphologically from blood eosinophils. Peripheral blood basophils and lamina propria mast cells were morphologically similar and expressed similar antigens. Monocytes and alveolar macrophages also expressed the same surface antigens.