As the humoral IgG2a response is a predictive parameter for the immunologic antitumor memory , we then compared Surek and Surek/HB304 vaccination with regard to melanoma rejection in vivo. Challenge with a lethal dose of viable melanoma cells three weeks after start of the immunization showed that the vaccination effect induced by Surek is indeed significantly enhanced when the trAb is combined with HB304 during the immunization phase. While 40% of mice survived in the Surek-immunized group, about 80% were effectively protected when both antibodies were used for vaccination (Figure 4C). Thus, the bonus effect of the combination approach appeared far more pronounced in terms of anti-tumor memory than direct tumor cell killing.