S19 RIBOSOMAL PROTEIN DIMER AS MONOCYTE CHEMOTACTIC FACTOR IN CHRONIC INFLAMMATION.

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The extracts of rheumatoid arthritis-synovial lesions from seven patients possessed a strong chemotactic activity for monocytes and a negligible one for polymorphonuclear leukocytes. These results are consistent with a prominent histological feature of the synovial lesion, the mononuclear cell predominant infiltration. The major monocyte chemotactic factor in the synovial tissue extracts was purified to a single protein peak in reverse phase HPLC with a C4 column. NH_2-terminal amino acid analysis of the initial twenty residues yielded a single sequence. Surprisingly, this sequence was completely identical to that of S19 ribosomal protein. The purified sample demonstrated two protein bands in SDS-PAGE with apparent molecular masses of 34 k and 68 k. These sizes were two and four times that of S19 ribosomal protein suggesting that the chemotactic factor would be a dimer or tetramer of S19 ribosomal protein cross-linked by factor XIIIa. A recombinant human S19 ribosomal protein was prepared as a fusion protein with a maltose binding protein in E.coli. After treatment with factor XIIIa, cross-linked recombinant S19 ribosomal protein exhibited the monocyte chemotactic activity although the untreated recombinant protein did not.