IL4 and oral lichen planus: In a study on the salivary levels of interferon-γ (IFN-γ) and interleukin-4 (IL-4) in a group of patients with oral lichen planus, the results indicated a significant increase in the levels of both cytokines.5 Another study showed that TGF-β suppresses the immune response to auto-antigens, and the severity of inflammation from lichen planus increases in areas with reduced TGF-β activity.6