Augmented photoswitching modulates immune signaling.

Reversible and non-invasive photoswitching of the immunosuppressive effect of a drug would be a very valuable tool for precisely regulating the immune system. Using a combination of protein borrowing and two-photon photoisomerization, we designed and synthesized derivatives of cyclosporin A. Here we demonstrate photoswitching of the local conformation within small molecules, which we used to modulate inhibitory potencies for cyclophilin, influence ternary and quaternary complex formations and regulate T-cell transcriptional activation in situ.