Bovine immunoglobulins and brucellosis. 3. Activity of IgG, IgG2 and IgM versus different commercial batches of Rose Bengal antigen.

The serological diagnosis of bovine Brucellosis by the Rose Bengal test has been disputed on account of the amount of active immunoglobulins and the results obtained in field trials. In order to try and explain these discrepancies, we have compared the activity of different commercial preparations of the Rose Bengal antigen for purified IgG1, IgG2 OR Igm dies. Two antigens which give the same titer for the Ig1 differ by a factor 8 in the titration of the IgM. Some antigens titer the IgG2, others, do not at all, or very little. Heifers in the 6th month of gestation were experimentally infected with Brucella abortus and half the animals showed "positive" from the 12th day with one antigen, whereas with another, they did not register until the 30th day. Heifers vaccinated at the age of 6-8 months with the B19 which still react to the Rose Bengal test 14 months later are 4 times more numerous with one of the antigens than with another.