Fig. 2.

T cells treated with a combination of IL-15 and IL-21 show enhanced antigen-specific cytotoxicity. Murine splenocytes were gp100/A2 TCR-transduced and cultured with IL-2, IL-15, IL-21 or IL-15 + IL-21 as described in legend to Fig. 1. Cytokine-stimulated T cells were co-cultured for 4 h with ⁵¹Cr-labelled target cells. Target cells included B16A2 cells loaded with human gp100 peptide (a), B16gp100/A2 cells (b) or B16A2 cells (c). Effector to target ratios and percentages of specific ⁵¹Cr-release are indicated in the figures. Mock-transduced T cells served as negative controls. Only in case of mock-transduced T cells cultured with IL-15 + IL-21 there was some background activity towards B16gp100/A2 (not towards B16A2 with or without gp100 peptide) up to 20% of ⁵¹Cr-release at E:T ratio’s of >40:1. At the moment of cytotoxicity assay, 2 weeks after start of culture, TCR-Vβ14 surface expression was around 40% (data not shown). Results are from a representative experiment out of 6 experiments with similar results