TGM2 and celiac disease: Studies showed that pro-inflammatory LPS and IFN-γ induced secretion of thioredoxin-1 (TRX) by macrophages was able to activate the extracellular TG2 in macrophages in vitro and that intravenous administration of TRX resulted in a rapid increase in TG2 activity exclusively in the small intestine in mice (i.e., this TRX-induced TG2 activity was not observed in other organs), suggesting that enhanced TG2 activity may be caused by inflammation in celiac disease [163].