Fig. 1 |. Masked IL-12 fully regains activity upon treatment with recombinant proteases.

a, Schematic of masked IL-12 in healthy tissues (no signalling) and in the tumour, with the mask being cleaved by various tumour-associated proteases. b, SDS-PAGE analysis of the cleavage of masked IL-12 variants by recombinant proteases. IL-12 (50 μg/ml; 0.84 μM), M-L₃-IL12 (0.84 μM) or M-L₂-IL12 (0.84 μM) were incubated with activated MMP2 (2 μg/ml), MMP9 (5 μg/ml) for 30 min at 37°C or with uPA (10 μg/ml) for 2.5 hr at 37°C. c,d, Dose-response relationship of phosphorylated STAT4 (pY693) with MMP2-treated M-L₃-IL12 (c) and uPA-treated M-L₂-IL12 (d) in preactivated primary mouse CD8⁺ T cells (n=2 per condition, technical duplicates). Data are mean ± s.e.m.; EC₅₀, half-maximum effective concentration; MFI, mean fluorescence intensity. Experiments were performed at least twice, with similar results. Representative data are shown.