Mechanism of T-cell help in the immune response to soluble protein antigens. I. Evidence for in situ generation and action of T-cell-replacing factor during the anamnestic response to dinitrophenyl keyhole limpet hemocyanin in vitro.

The involvement of a nonantigen-specific T-helper factor in the anamnestic immune response to dinitrophenyl keyhole limpet hemocyanin is demonstrated employing cultures of unseparated spleen cell populations. In such cultures of primed and boosted spleen cells, a good IgG anti-DNP response could be obtained if the hapten was presented on a heterologous carrier, provided that the homologous carrier was added simultaneously. T-cell depletion and reconstitution experiments show that such a factor, presumably identical with T-cell-replacing factor is produced by primed helper cells upon rechallenge and helps primed B cells, stimulated by soluble heterologous carrier hapten conjugates, to become IgG-secreting cells.