Regulation of human in vitro anti-hapten responses: demonstration of a carrier effect

Human peripheral blood mononuclear cells, tonsillar lymphocytes, or mixtures of allogeneic or autologous B and T cells from these tissues were stimulated in vitro with the soluble hapten:carrier complexes TNP-OA, TNP-KLH, TNP-Myo, or TNP-Lac. These complexes were able to induce TNP-specific, direct PFC during 5–6 days in culture. The response involved proliferating PFC precursor B cells, nonproliferating T helper cells, and radiosensitive T-suppressor cell precursors. Exposure to high concentrations of free or carrier-bound hapten resulted in the inactivation of PFC precursor B cells. Carrier specific suppressor T cells could be induced by priming with nonhaptenated carrier protein and were able to block the PFC response when added to fresh target cultures. The use of hapten:carrier complexes permits the characterization of distinct T-cell functions independently of the assay system for B-cell activation.