Abstract
Fresh bovine sera absorbed with sheep red blood cells (RBC) agglutinated RBC weakly sensitized with anti-RBC rabbit antibody, indicating the sera to be satisfactory as the source of conglutinating complement. Conglutinin was present in excess in these sera. Based on these observations we developed a conglutinating complement absorption (CCA) test using the conglutinating system of fresh bovine serum and sensitized RBC. Inactivated bovine sera were found to inhibit or enhance bovine complement and also to agglutinate normal RBC. These activities were readily eliminated by treating the sera with bovine complement and anti-RBC rabbit serum and then absorbing with RBC. This treatment was shown to be prerequisite for the bovine serum to be assayed by the CCA test. The CCA test was proven to be useful and practical for the assay of brucella antibody in bovine sera. The test was shown to be as sensitive and specific as the hemolytic complement fixation test. One of the advantages of the new CCA test is that the results can be readily read by the sedimentation pattern of RBC, whereas in the current CCA test the results are read by a rather cumbersome procedure in which the cells are centrifuged and briskly resuspended to distinguish strong conglutination from non-specific weak agglutination. The new CCA test was therefore readily adapted to the microtiter method. The method gave antibody titers agreeing well with those obtained by the tube method.
