TGM2 is a conserved M2 marker that is highly expressed in asthma. (A-B) TGM2 and CD68 expression was analyzed in bronchial biopsies of asthma patients (A) and lung sections of mice with asthma (B). Shown are representative sections stained for CD68 (blue) and TGM2 (red). Arrowheads indicate double-positive cells. (C) Airway wall tissue of asthmatic patients contains more TGM2⁺ macrophages than that of healthy controls. ***P < .0001. (D) Lung tissue of mice with asthma contains more TGM2⁺ macrophages than that of control mice. *P = .0286 by 2-tailed unpaired t test. (E) TGM2 is also expressed in monocytes as detected by FACS. Monocytes were gated according to their forward/side scatter (red); monocytes were left untreated or stimulated with IL-4. (F) Asthmatic patients showed significantly increased eosinophil counts (***P < .0001) and exhaled NO levels (***P = .0003). In blood samples of these patients, TGM2 levels in circulating monocytes were significantly higher in asthmatic patients than in healthy controls (***P = .0002 by 2-tailed unpaired t test with Welch correction). TGM2 MFI − bkgd = mean fluorescence intensity (MFI) detected with a primary polyclonal antibody subtracted by the MFI detected with control Igs. Eos indicates eosinophil counts.