IFNλ was incubated with CM for the indicated time at 37°C and 5% CO2 in the dark. As a loading control IFNλ was added to RPMI only. Reactions were stopped by adding western blot sample buffer and heat treatment (95°C, 10 min). Subsequently samples were used for western blot analysis. Quantification was performed using ImageJ and samples were normalized to the input control.