[Standardization of the complement fixation test (CFT) in brucellosis. II. The antigen].

The activity of cellular antigens and those as aqueous extracts prepared from 4 laboratory strains of Brucella abortus: 99, S-19, 119-3 and "Krotz" has been compared in this paper. The purpose of the studies was to select an antigen of the highest activity and to test it by the Polish Standard of anti-Brucella abortus serum. It was shown that cellular antigens are more active in CFT than aqueous extract antigens of the same brucella strain. Cellular suspension of Br. abortus strain S-19 was chosen for production of the domestic antigen. A chessboard system was used in standardization of this antigen. In the working dilution of the antigen in CF such an amount of it was used that gave the titre 250++ according to the Polish standard of anti-Brucella abortus serum. The multiplier 4 (1000:250) was obtained which serves to calculate CFT titres in terms of international units of the complement fixing antibodies (icftu) in 1 cm3 of the serum studied. In examinations of all species of farm animals by the standard CFT technique, 10-20 icftu were assumed as a doubtful result and greater than or equal to 20 icftu as a positive result. A definite excess of the antigen used in working solution limits the prozone range and permits to carry out CFT in mass diagnostic examinations initially using one lowest serum dilution.