Relationship Between Complement and Prothrombin

Abstract

Bordet was the first to recognize a relationship between thrombin and complement. Fuchs has recently claimed that the mid-piece of complement is identical with prothrombin. Since the complement content of plasma and serum are apparently the same, the change of prothrombin to thrombin does not seem to influence complement. A close association of prothrombin and thrombin with complement is indicated by: 1. Both complement and thrombin are non-specific. Complement obtained from one animal will react with the amboceptor and antigen of another species. Thrombin from various animals will clot fibrinogen irrespective of its source. 2. Both thrombin and complement, particularly the mid-piece, are associated with the globulin fraction of the serum proteins. 3. Prothrombin, thrombin, and complement are inactivated at 56°C, and the resulting serum or plasma becomes antithrombic and distinctly anticomplementary (the plasma more than the serum). 4. Serum or plasma treated with an emulsion of magnesium hydroxide becomes antithrombic (anti-clotting), and anticomplementary, with the effect more pronounced in the plasma than in the serum. 6. Calcium inhibits both complement and clotting. For the reactivation of prothrombin in oxalated plasma, there is an optimal concentration of calcium, below and above which clotting is retarded. Absence of calcium does not inhibit complement. That prothrombin is not identical with complement is indicated by: 1. Alumina cream will remove prothrombin from plasma but will not alter the complement content. 2. Patients have been found whose plasma is anticomplementary, but have a normal clotting time.