Poor ex vivo induction of T-cell responses to idiotype or tumor cell lysate-pulsed autologous dendritic cells in advanced pre-treated multiple myeloma

This study evaluated the feasibility of using dendritic cells (DCs) to generate, ex vivo, anti-tumor cytotoxic T lymphocytes (CTL) in patients with stage III multiple myeloma ( MM). Nucleated cells from eight patients who had received chemotherapy ( three of whom had undergone autologous hemopoeitic stem cell transplantation) were collected by apheresis. Their monocytes were enriched using counter-current centrifugation, differentiated into DCs which were further co-cultured with autologous CD8 lymphocytes to induce CTL. The DCs were pulsed either with the idiotypic paraprotein ( regarded as a tumor-specific antigen) or with autologous MM cell lysate before co-culture. Specific T-cell responses were measured in IFN gamma enzyme-linked immunospot and chromium release assays of autologous plasmocyte targets. A slight increase in IFNg secretion by T-cells was observed for two patients ( DCs pulsed with idiotypic paraprotein for one, MM cell lysate for the other). No or weak specific lysis of plasmocyte targets was observed in the chromium release assays. In conclusion, the T-cell response to pulsed DCs was very weak or absent. There are clinical and technical reasons that could explain, in part, this lack of response.