T cells from spleens of differentially vaccinated mice were stimulated in vitro with splenocytes that were loaded with melanoma-derived peptides . After 7 days, T cells were analyzed for expression of CD4, CD8, CD44 and CD62L. At least 4 mice were included in each group. (A) Representative diagram delineating the differentiation between different memory and effector T-cell compartments. (B) Quantitation of CD4+ T-cell subpopulations from differentially vaccinated mice. (C) Expression of CD137 on CD4+ T cells after in vivo immunization and restimulation with melanoma peptides. CD137+ cells were exclusively identified as CD44+ memory cells (not shown). (D) In the CD8+ T-cell population, an expansion of the memory compartment or a significant upregulation of CD137 was not induced by the combination approach. In all panels, columns represent mean values and SEM. Significances are also shown (Mann-Whitney).