Polyclonal IgG synthesis of mononuclear cells induced by the homopolymer of 4,6-dideoxy-4-formamido-alpha-D-mannopyranosyl units isolated from Brucella melitensis.

Brucella melitensis attaches selectively to B lymphocytes. The bacterium induces in vitro only a slight proliferation of mononuclear cells and inhibits the spontaneous IgG synthesis. In order to characterize these effects, the O-chain of the lipopolysaccharide of Brucella melitensis (a polysaccharide consisting of poly-4,6-dideoxy-4-formamido-alpha-D-mannoside) was prepared and its influence on lymphocyte functions tested. This compound had no effect on blast transformation whereas IgG synthesis of the cells was stimulated more than tenfold by the addition of the Brucella polymannoside.