Antigenic Competition Between and Endotoxic Adjuvant and a Protein Antigen

Dissociation of the anti-hapten and anti-carrier responses of mice injected with dinitrophenylated lipopolysaccharide

The quantitative and qualitative nature of the antibody responses of euthymic (normal, RML) and athymic (nude) mice injected with dinitrophenylated (DNP) lipopolysaccharide (LPS) was evaluated. Antibody responses to both the haptenic (DNP) and carrier (LPS) determinants were measured. On a quantitative basis, RML and nude mice stimulated with DNP-LPS produced only primary anti-DNP responses, whereas both primary and secondary anti-LPS responses were elicited by this conjugate. The failure of DNP-LPS to trigger secondary anti-DNP responses was not dependent on the amount of DNP-LPS given in the primary or secondary doses and could not be overcome by repeated injections of DNP-LPS. Also, the anti-DNP responses of RML mice injected repeatedly with DNP-LPS were restricted to immunoglobulin M antibodies whereas both immunoglobulin M and G anti-LPS responses were elicited. Nude mice also produced immunoglobulin G antibodies to the LPS determinants. These data showed a dissociation of the anti-hapten and anti-carrier antibody responses and suggested that different immunological signals were functioning in the respective anti-DNP and anti-LPS responses.

Influence of the antigenicity of Brucella preparations on modulation of the immune response to sheep erythrocytes

The relationship between the expression of surface antigenicity of inactivated Brucella and the immunostimulant properties on the sheep erythrocyte response was studied in mice. The agglutinogenic Brucella abortus B19S preparation was compared to two non-agglutinogenic preparations (B19R and PB), using the plaque-forming and rosette-forming cell tests. When Brucella and antigen were injected together, only non-agglutinogenic preparations, even used at low doses, were able to increase the plaque-forming and rosette-forming cell responses measured 4 days after immunization. When the interval between the previous injection of non-agglutinogenic preparations and that of the antigen increased or when they were injected 24 h after the antigen, the modification of those two responses was no longer observed. After day 4, for the simultaneous injection of Brucella and antigen, B19S and PB preparations induced the best responses; this effect was dose dependent. Thus, in the present experimental situation, the modification of the day 4 response appeared independent of those of the ensuing days.

Immunological responses of mice to native protoplasmic polysaccharide and lipopolysaccharide: functional separation of the two signals required to stimulate a secondary antibody response

Functional separation of the two signals involved in stimulating immunological responses was achieved through the judicious use of two natural bacterial antigens. Native protoplasmic polysaccharide (NPP) extracted from Escherichia coli was immunochemically identical to the lipopolysaccharide (LPS) extracted from the same organism. However, NPP was not endotoxic, not mitogenic, did not fix complement, and was immunologically independent of T cells. The NPP, which appeared to contain only the antigenic signal, could induce a primary antibody response in mice and could sensitize mice for a secondary response. However, the antigenic signal contained in NPP was insufficient to trigger a secondary response in mice primed with either NPP or LPS. LPS, containing both the antigenic and second signals, was required to trigger a secondary response in primed mice.