β1C-Globulin: an “Acute Phase” Serum Reactant of Human Serum

Acute phase human serum from various sources was found to contain elevated levels of β1C-globulin. Experiments designed to establish the relationship between this globulin and complement showed that, although β1C-globulin had physicochemical characteristics associated with both C′3 and C′4, serum lacking this globulin showed undiminished hemolytic complement activity. The serum fraction used for the isolation of C′4 contained no β1C, and similarly some serum fractions having concentrated C′3 activity (as this is customarily defined) contained no β1C. Neither red cells of other species nor incompatible human red cells removed this globulin from normal human serum. However, β1C-globulin was selectively affected by antigen-antibody complexes, Mycobacterium tuberculosis, Neisseria meningitidis and cortisone. The results suggest that β1C-globulin plays a part in physiologic response to stress.