Cellular responses to "brucelline INRA" during the experimental brucellosis of the mouse

"Brucelline INRA" is an aqueous extract of a rough strain of Brucella melitensis that is used to test cutaneous delayed hypersensitivity in man and animals. The cellular response of mice (either normal, or sensitized by a previous brucella infection) was investigated with local implanted "cell-traps" and by immunological testing in vitro. Brucelline markedly reduced the number of polymorphonuclear cells in the local infiltrate of sensitized animals during the early, nonspecific phase of the response. In vitro responses were dissociated; while brucelline depressed the incorporation of thymidine into lymphocytes, on controls as well as on sensitized animals, it induced an evident production of macrophage inhibitory factor. Since brucelline is a mixture of several molecular species, and antibodies to some of its components were present in sensitized animals, immunomodulation of these apparently paradoxical responses is probably the result of a combination of different mechanisms. These observations are discussed in the light of physiopathological features of the experimental brucellosis in mice.