The complement activity of canine serum

Quantitative studies have shown that the haemolytic activity of canine complement was in all essentials similar to guinea-pig complement. Canine serum which had been heated at 56° C. markedly enhanced the haemolytic activity of canine complement. The complement-enhancing power of heated canine serum was found to be increased with the concentration of serum up to 20%. Further concentration up to 50 % serum dilution, or the use of undiluted serum, resulted in a reduction of this effect.

Serum aliquots were either pro-complementary or anti-complementary to cn, depending on whether they were heated at 56 or 62° C.

Factors that possibly affect the complement-enhancement were investigated and evidence is presented which indicates that the electric charge on the protein particle is probably responsible for either the pro-complementary or anti-complementary serum activity; the mechanism of this, however, still remains obscure.

The present work shows also that canine complement can be used instead of guinea-pig complement for testing canine sera with virus antigen by the complement-fixation reaction, an advantage of this being that the use of canine complement permits the testing of canine sera which are anti-complementary to guinea-pig complement.

The data obtained are discussed in relation to canine complement and its specific activity.

The authors are indebted to Professor W. I. B. Beveridge for his constructive advice, to Dr R. R. A. Coombs for his helpful comments on the complement activity, and to Dr Christine E. Rice of the Animal Diseases Research Institute, Canada, who has generously supplied the zymosan.

Miss W. Barr and Miss M. Baker gave fine technical assistance throughout all the experiments. Miss M. Lambourne assisted in preparing the manuscript and graphs.