GUINEA PIG BETA-1C-GLOBULIN: ITS RELATIONSHIP TO THE THIRD COMPONENT OF COMPLEMENT AND ITS ALTERATION FOLLOWING INTERACTION WITH IMMUNE COMPLEXES.

Abstract

Summary Antibody was readily produced in rabbits against the β 1C -globulin of fresh guinea pig serum. This β 1C -globulin was founded by absorption studies to be antigenically and functionally related to the C′3c component of complement. Upon aging or treatment with immune complexes or zymosan, the β 1C -globulin in whole serum was converted to β 1A -globulin, a more slowly migrating protein in electrophoresis. The β 1C -β 1A -globulins of the mouse, rat and guinea pig were found to behave similarly in this regard. Fluorescent antibody to guinea pig β 1C demonstrated the presence of this component in Arthus reactions (including reactions in B10-D2 old line mice that are deficient in one of the C′3 group of components), and with antigen-antibody complexes that had been deposited in vessel walls from the circulation. Guinea pig β 1C -globulin was converted to an electrophoretically slower β 1A form, by sheep erythrocytes sensitized by antibody and the first, fourth and second components of guinea pig complement (EAC′1a,4,2a). The inactivation of C′3c in the fluid phase and conversion to β 1A appeared to be separable events. The conversion process was completely inhibited by 0.02 M benzoyl-L-arginine methyl ester (BAMe) or 0.002 M p -toluene sulfonyl-L-arginine methyl ester (TAMe), and partially inhibited at 0°C or by 0.02 M diisopropylfluorophosphate. Conversion appeared not to require activated first component of complement, or the C′3b component, but occurred only in the presence of activated second component. The data do not allow a clear determination of what substance directly mediates conversion. Of note, immune-adherence activity was found in the absence of detectable conversion. Conversion of β 1C -globulin to the β 1A form during the aging of whole serum did not occur in the absence of divalent cations. The data suggest that the aging process may be mediated by a substance which accumulates slowly in the serum, and which interacts with complement in a manner similar to that observed with antigen-antibody complexes.