Human Interferon-lambda1/Interleukin-29 is produced by human peripheral blood mononuclear cells (PBMC) and dendritic cells, with antiviral, anti-proliferative and antitumor effects. Human Interferon-lambda1/Interleukin-29 is a member of the interferon lambda family (also known as type III interferons), whose members are distantly related to both the type I interferons and members of the IL-10 family. IFN-λ1 also has important immunoregulatory property, especially with regard to the T helper type 2 (Th2) response.