Different allotypes of C3 degrade at different rates

To determine whether different forms of C3 degrade at different rates, we compared two strains of mice with a B10 background. The only difference was that one is C3A, while the other is C3B. These strains allow comparison of C3A and C3B without the added complication of differing C3 convertases. Sera from the two strains were incubated with zymosan and the degradation products were detected by immunofixation following electrophoresis in agarose. The rate of degradation of mouse C3B was more rapid than that of C3A. Differences in the rates of degradation could not be explained by differing concentrations of C3. We suggest that the genetic differences in C3 determine the decay rate following activation via the alternate pathway.