Monoclonal antibodies defining shared human macrophage-endothelial antigens

We have selected several monoclonal antibodies (mAbs) produced using human rheumatoid arthritis (RA) synovial macrophages (mφs) as immunogen. Of these, mAbs 8H2, 10G7 and 10G9 showed cross reactivity with endothelium. suggesting common antigens between these cell types. We have determined the spectrum of reactivity of these mAbs on hematopoietic cell lines, peripheral blood cells, and inflammatory and non-inflammatory tissues by immunohistochemistry. MAb 8H2 does not react with the myeloid cell lines HL60 (myelocytic), U937 (histiocytic lymphoma), and K562 (erythroleukemia), or with peripheral blood cells. In normal and inflamed tissue sections, mAb 8H2 reacts with mφs and endothelial cells. In contrast. mAb 10G7 does not react with peripheral blood cells, but reacts with HL60, U937, and K562 cell lines, as well as with mφs and endothelial cells in inflamed and noninflamed tissues. MAb 10G9 does not react with myeloid cell lines, but reacts with monocytes and platelets in peripheral blood. In both normal and inflamed tissues, mAb 10G9 reacts with mφs and endothelial cells. The antigens identified by these three mAbs were characterized biochemically, by enzymatic digestion of RA synovial tissue mφs followed by a cellular ELISA, as well as by reactivity of the mAbs with NIH-3T3 cells genetically engineered to express known myeloid antigens. These mAbs reacted with protein or glycoprotein antigens distinct from the known myeloid antigens CD13, CD14, CD33, CD34, CD36, and c-fms. These mAbs should prove to be a valuable tool for studying mφs and endothelial cells and their shared antigenic determinants.