IL-28A, also known as interferon lambda 2 (IFN-lambda2), is distantly related to type I interferons and the IL-10 family of cytokines. Along with IL-28B (IFN-lambda3) and IL-29 (IFN-lambda1), IL-28A belongs to the IFN-lambda family of type III interferons. Expression of the IFN-labmda family of cytokines is triggered by virus infection. All three members bind to a receptor complex composed of an IFN-lambda R1 subunit (also called IL-28R alpha) and IL-10R2 subunit (also called IL-10R beta), inducing antiviral activity.