STUDIES ON THE ANTIGENIC PROPERTIES OF COMPLEMENT

Abstract

Sensitized sheep erythrocytes exposed to guinea pig complement (C'') were agglutinated by immune sera from rabbits injected with guinea pig globulin or with sensitized sheep stromata laden with guinea pig C''. Sensitized sheep erythrocytes exposed to only the first component of C'' were not agglutinated by these immune sera, whereas cells exposed to the first and 4th components together were agglutinated. The immune sera absorbed with sensitized erythrocytes in complex with the first and 4th components did not subsequently agglutinate that complex with which it was absorbed or that complex exposed additionally to the 2d C component. It is concluded that the 4th component of C is fixed to sensitized erythrocytes in conjunction with the first component and that the 4th component is antigenic as indicated by its agglutinogenic property, whereas neither the first nor the 2d components could be shown to be agglutinogenic. An additional agglutinogen was found in the material fixable from guinea pig serum to sensitized erythrocytes in complex with the first, 4th, and 2d C components; and this additional agglutinogen appears to be distinct from the hemolytically active 3d component of C''.