Immunoglobulin Components in Crystalline Ceruloplasmin and Anticomplementary Activity1

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Abstract
The presence of small amounts of γG‐globulin and of γM‐globulin components have been demonstrated in once‐crystallized ceruloplasmin preparations. These immunoglobulin impurities appear to be largely removed by repeated crystallization or by chromatographic procedures utilizing SE‐cellulose and hydroxylapatite. The anticomplementary activity of such material, although free from immunoglobulins, is comparable to that of once‐crystallized ceruloplasmin. This activity of ceruloplasmin differs markedly from that of γG‐globulin in that human serum albumin abolishes the activity of ceruloplasmin, and increases in the concentration of ceruloplasmin do not effect parallel increases in anticomplementary activity. Crude ceruloplasmin preparations possess both thermolabile and thermostable anticomplementary factors but crystalline material contains only the latter type. Complete or partial removal of copper modifies but does not abolish the anticomplementary activity of ceruloplasmin. These results suggest that the anti‐complementary activity of ceruloplasmin is a property of the protein and is not due entirely to its component copper or to the presence of immunoglobulin impurities.