Conserved macrophage alternative activation gene and protein signatures reveal TGM2 as the most stable marker. (A) Up-regulation of TGM2 protein by M2 activation can be confirmed by Western blot in different human macrophage culture models (M-CSF, GM-CSF, and AS). Analysis of Mannose receptor (MRC1) and Actin expression were used as alternative activation and loading controls, respectively. In addition, expression of transferrin receptor (TFRC) and annexin A4 (ANXA4) was determined. (B) In mouse macrophage protein samples, IL-4–induced Tgm2 up-regulation can be confirmed in thioglycollate- (mThioMΦ) and Biogel (mBioMΦ)–elicited peritoneal macrophages and BM-derived macrophages (mBMMΦ). Mrc1, Tfrc, Anxa4, and Actin expression was analyzed in parallel. (C-D) Time-course analysis of TGM2/Tgm2 in human AS macrophages (C) and mouse ThioMΦ (D). (E-F) Transglutaminase activity was determined in human AS macrophages (E; n = 3) and mouse ThioMΦ (F; n = 4). *P < 0.05. Shown are means ± SEM. Transglutaminase activity was normalized to the amount of protein and to the unstimulated control.