Revised Manuscript Received January 25, 1988 abstract: A protein chemotactic for peripheral bloodmonocytes (SMC-CF) of potentialimportance in their recruitment to the arterial intima inatherogenesis was purified from serum-free medium conditioned by cultured baboon aortic medial smooth muscle cells. The purification of SMC-CF was monitored by a filter assay using human peripheral blood mononuclear cells and was achieved by batch separation on a cation-exchange gel followed by gel permeation chromatography, ion-exchange high-performanceliquid chromatography (HPLC), and reversed-phase HPLC. The overall recovery was approximately 10% of the initial activity and yielded 0.5-1 pg of SMC-CF/L of conditioned medium. On analytical sodium dodecyl sulfate-polyacrylamide gel electrophoresis, SMC-CF migrated as a monomeric protein with an apparent molecular weight of 14 500. A dose-dependent relationship was observed between SMC-CF concentration and monocyte chemotacticactivity, with maximal and half-maximal biologic activity being observed at approximately 5 and 0.1 nM, respectively. Cultured baboon aortic smooth muscle cells alsoexpress the genes for both the A and B polypeptide chains of platelet-derived growth factor, which has been reported to be chemotactic for blood monocytes and neutrophils [Deuel, T. F., Senior, R. M., Huang, JS, & Griffin, G. L.(1982) J. Clin. Invest. 69, 1046-1049]. Amino acid compositionanalyses indicate that SMC-CF is not derived eitherfrom polypeptide chain of this growth factor or from certain potentially chemotactic connective tissue proteins.

^ Enhanced recruitment of peripheral blood monocytes to the arterial intima is a feature of both human and experimental atherosclerosis (Duff et al., 1957; Still & O’Neal, 1962; Gerrity et al., 1979; Schaffner et al., 1980; Stary, 1980; Lewis et al., 1982; Joris et al., 1983; Schwartz et al., 1985a). Intimal monocyte-derived macrophages are thought to be important in atherogenesis since they perform several major functions related to tissue injury and repair [reviewed by Schwartz et al.(1985b, 1986)]. In addition to being precursors of many of the cholesteryl ester-rich foam cells found in intimal plaques,