THE ANTIBODY MY4 RECOGNIZES CD14 ON PORCINE MONOCYTES AND MACROPHAGES

Several monoclonal antibodies directed against the human CD14 antigen have been established. We now report that the antibody My4, but not LeuM3, reacts with porcine monocytes. Among porcine peripheral blood mononuclear cells (PBMC), 14.6% of the cells stain with the CD14 antibody My4, which is similar to the percentage obtained with the antiporcine monocyte antibody 74-22-15. Two-colour immunofluorescence reveals that My4 and 74-22-15 antigens are coexpressed on the same cells, and cell sorter-purified My4(+) cells exhibit the morphology of monocytes. Whole blood analysis (which also shows staining of granulocytes) reveals that the average percentage of My4 + monocytes amongst all leucocytes is 5.8% with 580 cells/mu 1. Furthermore, porcine peritoneal macrophages (PM) and alveolar macrophages (AM), both stain for My4, with a four-fold lower level on AM. Treatment of cells with phosphatidylinositol-specific phospholipase C decreases My4 staining, but does not affect staining with antibody 74-22-15. Immunoprecipitation with the My4 antibody from surface labelled pig mononuclear cells demonstrates a 54 kDa band similar to human CD14, and Western blotting with pig serum demonstrates two bands similar to the alpha and beta forms of human soluble CD14. Finally, the My4 antibody is capable of blocking lipopolysaccharide- (LPS)-induced interleukin-6 production in isolated PBMC. These data show that the My4 antibody recognizes genuine CD14 on porcine monocytes and macrophages.