In contrast, a moderate negative correlation was found between the percentages of circulating MAIT cells and the levels of serum CEA in the patients with advanced stage of CRC (R = −0.5559, P = 0.0245, Fig. 3f), but not in those with early stage of CRC (R = −0.4050, P = 0.1197). Here, CEACAM5 is linked to colorectal carcinoma.