Various Brucella antigens, such as gamma-irradiated vaccine (2x10r´), heat-killed organisms (60C -30 min.) and from dissociated variants (SR or R form), were employed in immunizing rabbits and .goats in routine procedures. Anti-Brucella sera thus obtained were compared with each other as well as .normal serum as to their brucellacidal activity in vitro, mouse protecting ability, and effect on the respiration of Brucella organism.
1. Regardless of the kind of animals and antigens used in producing the anti-Brucella serum, the in vitro brucellacidal activity of immune sera was distinguishedly reduced in comparison with that of normal sera so far as the agglutination titer was higher than a certain level (1 : 320).
2. In the comparative mouse protecting test, the Brucella-immune sera exhibited a considerably curing .effect, while normal serum and antibiotics (chloramphenicol, streptomycin and tetracycline) did not.
3. Brucella melitensis showed a markedly reduced respiratory rate in the presence of anti-serum, -compared with that in i lae presence of normal serum, for complement together with antibodies exerted .the depressive effect on the bacterial oxidative metabolism. Antibiotics, however, did not give any .differences on the oxygen uptake rate of Brucella cells.
4. The significance of artificial pas3ive immunity in brucellosis was discussed with reference to the results of this experiment.
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