Background: Gc protein has been reported to be a precursor of Gc protein-derived macrophage activation factor (GcMAF) in the inflammation-primed macrophage activation cascade. An inducible beta-galactosidase of B cells and neuraminidase of T cells convert Gc protein to GcMAF. Materials and Methods: Gc protein from human serum was purified using 25 (OH) D] affinity column chromatography and modified to GcMAF using immobilized glycosidases (betagalactosidase and neuraminidase) The sugar moiety structure of GcMAF was characterized by lectin blotting by Helix pomatia agglutinin. The biological activities of GcMAF were evaluated by a superoxide generation assay and a phagocytosis assay. Results: We successfully purified Gc protein from human serum. GcMAF was detected by lectin blotting and showed a high biological activity. Conclusion: Our results support the importance of the terminal N-acetylgalactosamine moiety in the GcMAF-mediated macrophage activation cascade, and the existence ofconstitutive GcMAF in human serum. These preliminary data are important for designing small molecular GcMAF mimics.

Inflammation induces chemotaxis and activation of macrophages, which thus leads to immune development (1). Macrophages are known to play a critical role in antitumor immunity (2). They can also infiltrate tumor tissues and are found at most tumor sites (2, 3). MeanWhile, Group specific component (Gc protein), also known as Gc globulin or vitamin D3-binding protein, is a serum protein which has been reportcd as a precursor for macrophage activating factor (4). The role of Gc protein in inflammation-mediated