Cross-immunity between Brucella melitensis and Mycobacterium tuberculosis; intracellular behavior of Brucella melitensis in monocytes from vaccinated animals.

A non-specific element has been demonstrated in the resistance of monocytes derived from immunized rabbits. Vaccination by BCG or by an effective anti-brucellosis reagent induces protection in either case against both Mycobacterium tuberculosis and Brucella melitensis when studied by the monocyte culture method. The activity of the antiserum required to demonstrate the resistance of the monocyte is not affected when the agglutinating action of the anti-Brucella rabbit serum is removed by absorption. The ability of the monocytes from specifically immunized rabbits to retard the growth of virulent Brucella was demonstrated, not as an all-or-none phenomenon, but in the light of the unrestricted bacterial multiplication which occurs in monocytes from normal animals.