The purpose of this study was to determine whether a combination of two anti-idiotypic antibodies that mimic the high molecular weight proteoglycan antigen found on most melanoma tumors was capable of enhancing cellular immunity in vaccinated high-risk patients with melanoma. Twenty-eight stage I-IV high-risk patients with melanoma were immunized with a mixture of variable concentrations of MELIMMUNE-1 and MELIMMUNE-2, along with the adjuvant SAF-m, using two immunization schedules. Peripheral blood mononuclear cells were collected before the first immunization and 4 weeks after the final immunization and tested for in vitro proliferation to MELIMMUNE-1 and MELIMMUNE-2 and for cytotoxicity against 51Cr-labeled target cell lines. Additionally, supernatants from in vitro proliferation cultures were tested for interleukin 10 and IFN-gamma levels. Significant in vitro proliferation to MELIMMUNE-1 and MELIMMUNE-2 were observed in postimmunization samples but not in prevaccination samples. The mean stimulation index for MELIMMUNE-2 (33.7 +/- 0.6) was significantly higher than that for MELIMMUNE-1 (13.9 +/- 0.3; P < 0.025). Supernatants obtained from 78% of the in vitro stimulated cultures pre- or postvaccination contained significant levels of interleukin 10 (range, 0.43-142 pg/ml), whereas IFN-gamma levels were elevated in 53% of postvaccination samples (range, 3-245 pg/ml) but not prevaccination samples. More importantly, we were able to generate specific CTL responses in 43% of the patients, which correlated with elevated IFN-gamma levels. These results indicate that MELIMMUNE enhances cell-mediated immunity in patients with melanoma.