Because a similar increase of Th1 cytokines was seen in all trAb-vaccinated groups (Figure 4A), the combination approach had no impact on the Th1 response, which is instrumental for effective tumor protection [27, 28]. The simultaneous upregulation of Th2 cytokines in all groups where Th1 cytokines were induced was not unexpected since Th2 cytokines are required for priming Th1 responses [34, 36, 37]. A clear hierarchy, however, was detected for the humoral immune response induced by the different antibodies (Figure 4B). Thus, the improved immunologic memory observed after vaccination with trAbs combined with CTLA-4 blockade correlated with increased serum titers of melanoma-reactive IgG2a antibodies. Indeed, humoral immunity has been shown to be relevant for tumor protection in vivo . The finding of CD4+ rather than CD8+ memory cells after combined vaccination (Figure 5) supports this concept.