A NEW MACROPHAGE DIFFERENTIATION ANTIGEN WHICH IS A MEMBER OF THE SCAVENGER RECEPTOR SUPERFAMILY

The antibodies Ki-M8, Ber-Mac3, GHI/61 and SM4 define a human macropha ge-associated antigen with a relative molecular mass of 130000 which w e designate M130. The protein was purified by immunoaffinity chromatog raphy and an N-terminal and three internal amino acid sequences were o btained. A cDNA fragment was initially obtained by polymerase chain re action (PCR) using reverse-translated primers. Several variant cDNA cl ones, derived from alternative spliced messages, were obtained from a lipopolysaccharide-stimulated human monocyte library and were sequence d. The relative abundance of these variants was evaluated by a series of overlapping PCR reactions. The size of the most representative cDNA is 3.7 kb and closely agrees with the mRNA size of 3.8 kb determined by Northern blot analysis. The membrane protein encoded contains a lea der peptide of 40 residues, a putative extracellular domain of 1003 re sidues, followed by a hydrophobic segment ot 24 residues and a cytopla smic domain of 49 residues. The extracellular domain was found to cont ain nine repeating elements, of about 110 residues, which are similar to those of the scavenger receptor superfamily.