The Purification and Reactivity of the First Component of Complement from Guinea Pig, Human and Canine Sera

Abstract

A simple procedure for separation and purification of the first component of guinea pig complement is described. The product has high specific reactivity, low protein content and minimal content of other complement components. The formation of EAC1 using sheep erythrocytes sensitized with purified IgG was greater at 0°C than at 37°C. In contrast, the formation of EAC1 using sheep erythrocytes sensitized with IgM proceeded more effectively at 37°C than at 0°C. Preliminary results are presented on measurements of C1 by immune adherence as well as by immune hemolysis. Estimates of the number of molecules that are required for a 50% endpoint in each of these two reactions were 2 and 10 molecules per erythrocyte, respectively. Certain problems concerned with the exact definition of the molecular weight of C1 in native serum are discussed.