A modified complement fixation test that is subject to minimal anti-complementary activity by sheep serum

Abstract

A warm complement fixation test that will detect antibody in sheepserum in the virtual absence of anti-complementary activity is described. Sheep antibody-antigen complexes were detected by fixation of sheep complement. Sheep serum, heparinized or Mg⁺⁺—EGTA plasma was used as the source of sheep complement. Sheep-antibody-sensitized human erythrocytes were used as the haemolytic indicator cells for sheep complement. As the modified complement-fixation test was performed in the presence of Mg⁺⁺—EGTA, sheep C probably reacts with sheep Ab-Ag complexes by a different mechanism than does guinea-pig complement.