In contrast, the sampling of previous studies on the relationship between atherosclerosis and IDO1 usually ignored patients with myocardial infarction.26,33,34 The results showed that the expression and activity of IDO1 and TDO were increased in the early atherosclerosis stage (grade I, II), but the increase did not continue in advanced atherosclerosis (grade III). Here, TDO2 is linked to myocardial infarction.