The IgG anti-DNP antibody response to DNP-POL was explored in mice in an adoptive transfer system. The adoptive secondary IgG anti-DNP response required the presence of T cells. The IgG anti-DNP response to DNP-POL could be obtained in the irradiated recipients transferred with DNP-primed B cells if the recipients had been primed with either carrier or unrelated antigens 5 days before the cell transfer. Passive transfer of DNP-primed B cells plus T cells activated by carrier resulted in a high IgG anti-DNP response to DNP-POL. Passive transfer of DNP-primed B cells plus either T cells activated by unrelated antigens or unactivated T cells also resulted in a low but appreciable IgG anti-DNP response. Moreover, there are qualitative differences among these IgG anti-DNP responses. The IgG1, IgG2a, and IgG2b responses to DNP-POL were induced only in the carrier-primed recipients given DNP-primed B cells. By contrast, the IgG3 response to DNP-POL could be induced in the KLH-primed recipients receiving DNP-primed B cells.
These results indicate that the IgG anti-DNP responses to DNP-POL are induced through at least two different pathways; one involves a collaboration between carrier-specific T cells and hapten-specific B cells, and the other involves an interaction between noncarrier-specific T cells and hapten-specific B cells.