Mechanisms of prozone formation in agglutination reaction

Natural and artificially induced inhibition of agglutination, in the presence of adequate agglutinating antibody, has been demonstrated using Brucella abortus as antigen and sheep serum as the source of antibodies.At least three types of inhibition have been demonstrated: (a) due to a heat-labile component, found in both normal and immune sera, which is probably complement, (b) due to a heat-stable component which sediments with 7S-globulins and migrates electrophoretically with the fast gamma-globulins, (c) induced by heating serum at 56 °C for prolonged periods or 60 °C for shorter periods. The latter inhibition appears to be due to complex formation of IgM with other serum proteins, which results in inhibition of the agglutinating, but not binding, capacity of this immunoglobulin.The extent to which any or all of these phenomena may be demonstrated varies with the time (and probably activity) of an infection, and may allow more precise assessment of the stage of infection, particularly in chronic diseases.

Demonstration of Complement Fixing Antibody in the Sera of Cattle Vaccinated with Combined Living Blackleg-anthrax Vaccine

Complement fixing antibodies could be detected in the sera of cattle vaccinated with combined living blackleg-anthrax vaccine by modified complement fixation tests. Conventional direct complement fixation tests with bovine antibody-antigen systems often caused false negative reactions; however, in the modified test, when guinea pig complement was supplemented with fresh unheated normal rabbit serum, positive reactions were obtained and the sensitivity of the test was increased without loss of specificity.