This is in line with a recent study reporting an increased production of IL-22 in peripheral blood mononuclear cells (PBMCs) from nonallergic non-asthmatic and allergic asthmatic patients after treatment with diesel exhaust particle (DEP)-PAH and Benzo[a]pyrene (B[a]P) (Plé et al., 2015). Here, IL22 is linked to pulmonary arterial hypertension.