2000 年 28 巻 2 号 p. 81-89
N-Glycan structures of Type I cryoglobulin in 3 different samples are reported in detail. The three sample cryoglobulins were purified from sera of monoclonal immunoglobulin G (IgG) 1-κ type cryoglobulinemia: two of them from patients with multiple myeloma (cases 1 and 2) and one from a patient with Sjögren's syndrome (case 3). Asparagine-linked glycan portions of these cryoglobulins were released by digestion with glycoamidase A (from sweet almond), and the reducing ends of the N-glycans were reductively aminated with 2-aminopyridine. The derivatized N-glycans were separated and structurally identified by a multi-dimensional mapping technique on high performance liquid chromatography (HPLC) columns. The HPLC profiles of N-glycans from these patients were compared with that profile from healthy persons. The N-glycan molecules from the 3 different IgG proteins revealed individually abnormal profiles. A glycoform containing 2 galactose residues predominated in case 1. In contrast, no galactose was found in the predominant glycoforms in cases 2 and 3. Moreover, an unusually high content of bisecting N-acetylglucosamine characterized one of the predominant glycoforms in case 2. In spite of these striking N-glycan abnormalities, no clear mechanism that could cause cryoglobulinemia was found.
