Antibody formation in the mouse induced by hapten-carrier complexes.

The influence of hapten, carrier and their ratio in a complex on T-cell helper stimulation and antibody formation against the dinitrophenyl (DNP) hapten was studied. Complexes of DNP with bovine serum albumin (BSA), bovine gamma-globulin (BGG), isologous mouse immunoglobulin (MIG) and polyvinylpyrrolidone (PVP) as carriers were used. Optimal antibody formation against DNP was obtained with complexes with an intermediate hapten:carrier ratio (DNP 16-minusBSA, DNP 43-minusBGG and DNP 48-MINUSMIG). DNP-PVP complexes were not active either in the primary or in the secondary response. The anti-BSA titre was independent of the number of DNP groups on the complex used for immunization. Inhibition of DNP-plaque formation by spleen cells of immunized mice shows an increase of the inhibitory capacity of the complex with the increase of the hapten-carrier ratio. DNP 16-minusPVP was the only PVP complex which was inhibitory. These results suggest that helper cells involved in the antibody formation against BSA and DNP are reactive with different parts of the complex. Priming of mice with carrier or complex after cyclophosphamide (Cy) treatment followed by a secondary injection with complex 10 days later gave strong indications that there is a greater involvement in stimulation of helper T cells by determinants of the complex (new antigenic determinants (NAD) or NAP-DNP groups) or DNP, than by true BSA determinants. This holds for both the IgM and IgG responses.