IL12B and viral infectious disease: IL-12 is composed of p35 and p40 subunits, which are encoded by the IL12A and IL12B genes respectively.[15] The IL12B gene on chromosome 5 may affect the production of IL12,[16] which plays a critical role in the elimination of virus-infected cells.[17] IL12R is composed of two subunits, which are encoded by the IL12RB1 and IL12RB2 genes.[18] The IL12RB1 gene is located on chromosome 19p13.1 and encodes the ligand-binding chain of IL12R.[19] Genetic variations in the IL-12 and IL12R genes were associated with viral infection, such as hepatitis B virus (HBV) and hepatitis C virus (HCV).[17,20]