[Influence of the immune response by bacterial antigens. II. Effect of Vi-antigen on the IgM response against sheep erythrocytes].

Vi-antigen enhances the IgM response against sheep erythrocytes in vitro, in contrast to in vivo. This is true for both the specific and unspecific (background) response. In the presence of 10 micrograms Vi-antigen the IgM response reaches already after 3 d the optimum. After separation or elimination of the greatest part of macrophages, Vi-antigen stimulates the humoral immune response not only in vitro but also in vivo. The influence of Vi-antigen is optimal, if the Vi-antigen were added during the first 24 h of the culture. The influence is demonstrable however still after later addition. The effect of Vi-antigen is partially explicable via stimulation of the IL 1 production in the macrophages.