Cryo-EM helps engineer enhanced IL-10Interleukin-10 (IL-10) binds to the IL-10 receptor (IL-10R), comprising two high-affinity α chains and two low-affinity β chains. Depending on the cellular context of its recognition, IL-10 can either suppress or activate immune responses. This pleiotropic behavior has complicated efforts to use IL-10 as an anti-inflammatory agent. Saxtonet al.generated a high-affinity version of IL-10 (super-10), which allowed them to visualize IL-10 in complex with both IL-10Rα and IL-10Rβ by cryo–electron microscopy (cryo-EM). This enabled them to engineer additional variants of IL-10 with variable IL-10Rβ–binding affinities. Some of the partial agonists exhibited biased actions on myeloid cells, which exhibited anti-inflammatory properties without concomitant CD8 T cell activation. These findings may serve as a blueprint for future enhanced cytokine–based therapeutics.Science, this issue p.eabc8433