[Comparative studies between different methods for demonstrating blocking antibodies in experimental Br. melitensis...

In the course of 4 years 4624 serums of 34 sheep and 4 goats experimentally infected with Br. melitensis biotype 1 and biotype 3 in a chronic phase of the Brucella infection process and 2792 serums obtained from part of the same sheep in acute and subacute phase of Brusella infection were investigated. In was established that Coomb's test and the cysteine test show greater constancy in proving the existence of blocking antibodies. They are followed by the Brucella blocking test after Renoux and the mercaptoethanol test. In the complement binding reaction participate mainly mercaptoethanol-sensitive antibodies, while in the presence of blocking (mercaptoethanol resistant) antibodies the complement binding reaction is characterized by binding a smaller amount of the complement. Cold complement binding leads to increased titers of complement binding antibodies mainly in respect to blocking antibodies. Positive hemocultures are established more often in case of mercaptoethanol-sensitive agglutinins in high titers, while positive urocultures--in case of high titer reaction of complement binding, in case of higher titers of blocking antibodies or in case of positive complement binding reaction and higher content of blocking (mercaptoethanol resistant) antibodies.