ARG1 and inflammatory response: In the current study, we clearly demonstrated an exacerbated pulmonary immune response in mice upon co-exposure to MWCNTs and HDM extract which was characterized by a synergistic increase in eosinophilic inflammation in addition to increased phosphorylation of STAT-6, and increased expression of ARG-1 protein and Arg-1, Cc11 and Col1a1 mRNAs.