CD28 and neoplasm: To test whether genetic ablation of specific Notch ligands in DCs affected cytokine secretion patterns, we evaluated IFN-γ and IL-4 production in tumor-infiltrating T-cells by ELISPOT assay following restimulation with CD3/CD28 antibody activator beads or with LLC tumor antigenic MHC class-I-restricted peptide MUT1 loaded on autologous splenocytes.