IL-26 is a member of the IL-10 family first identified in T cells transformed with HSV (Herpesvirus saimiri). Its gene is expressed almost exclusively in T cells and is overexpressed upon virus transformation. IL-26 has been grouped as a TH17 cytokine as its expression has been found with cells expressing RORγt. Although not much is known about its biological functions, IL-26 is believed to be pro-inflammatory and targets epithelial cells. Its receptor is made up of the subunits IL-20R1 and IL-10R2 whose activation initiates STAT1 and STAT3 activation. Currently, no mouse counterpart to IL-26 has been identified.