Immunohistochemical staining of DC, tumor, and fusion cells. (A) Autologous DCs were generated from adherent mononuclear cells isolated from a leukapheresis collection. DCs were cultured with GM-CSF and interleukin-4 for 5 days and then with tumor necrosis factorα for 48-72 hours. DC preparations were analyzed for expression of costimulatory molecules. DC expression of CD86 (red) is shown (×60). (B) Patient-derived myeloma cells were cultured in RPMI 1640 complete medium and were analyzed for expression of the tumor-associated antigens CD138 and CD38. Tumor expression of CD38 (red) is shown (60×). (C) Fusion cells were generated by coculture of DCs and myeloma cells in the presence of polyethylene glycol. Fusion cell preparations were analyzed for coexpression of the DC-derived costimulatory molecule CD86 (blue) and tumor-associated antigen CD38 (red).