a, Schematic representations of DR-18 (left) and yeast-display directed evolution process (right). b, Representative histogram assessing staining for IL-18Rα (100 nM, left) and IL-18BP (200 nM, right) by flow cytometry of yeast display library after each round of selection. c, The sequences and dissociation constants (KD) of clones summarized for selected DR-18 variants, with differences from wild-type IL-18 indicated for each mutant at the given amino acid position (top). Green shading highlights converging residues to form consensus sequence (bottom). KD measurements are shown for binding of mIL-18 and DR-18 variants to IL-18Rα and IL-18BP measured by SPR. –, not tested; NBD, no binding detected. d, Quantification of intracellular IFN-γ staining in splenic NK cells stimulated with IL-18, CS1 or CS2 in the presence of IL-12. e, Quantification of intracellular IFN-γ staining in splenic NK cells stimulated with IL-18 or CS1 or CS2 in the presence of IL-12 and varying concentrations of IL-18BP. Data are representative of three independent experiments (d, e) with n = 3 mice per condition and presented as mean ± s.e.m.