Characterization of a novel myeloid antigen regulated during differentiation of monocytic cells.

The monoclonal antibody HC1/6 generated against phorbol 12-myristate 13-acetate-treated U-937 cells recognizes a new cell surface antigen with a broad relative molecular mass ranging from 100 to 150 kDa. This antigen is also present on monocytes, platelets and endothelial cells and is weakly expressed by granulocytes. In contrast, it is absent from T, B and erythroblastoid cells. The antigen HC1/6 is also expressed by normal tissue macrophages in tonsil, lung and kidney, as well as in skin biopsies from pathologies such as sarcoidosis and lepromatous leprosy. The expression of the HC1/6 antigen is increased up to 5-fold when U-937 (promonocytic) and HL-60 (myelomonocytic) cell lines are stimulated with phorbol 12-myristate 13-acetate. Conversely, the expression of the HC1/6 antigen is down-regulated in monocytes upon treatment with interferon-gamma. These findings are discussed in relation with other myeloid cell surface markers.

Characterization of a CD11c-reactive monoclonal antibody (HC1/1) obtained by immunizing with phorbol ester differentiated U937 cells.

A mouse monoclonal antibody (HC1/1) specific for a differentiation marker of human monocytes and granulocytes has been generated by using as immunogen the monocytic cell line U937 differentiated with phorbol esters. This differentiation antigen has been characterized as the p150/95 member of the CD11 family of glycoproteins by cellular distribution studies, immunoprecipitation and competition experiments with MAb 3.9 specific for the CD11c antigen. Immuno-alkaline phosphatase staining of normal tissue sections with the HC1/1 MAb demonstrated that the CD11c antigen is a useful macrophage marker. Furthermore, the MAb HC1/1 stains specifically populations of macrophages on skin and lymph node sections from different pathologies such as Sarcoidosis, Granuloma annulare, Lepromatous leprosy and Toxoplasmosis.