Considering that DOR expression levels on several immune cells in MLNs were reduced in colitis mice, and that of macrophages was further decreased by KNT-127-treatment, detailed analyses including determination of the protein levels in isolated cells rather than mRNA levels in whole tissues may be required to evaluate the effect of DOR-signaling and/or DSS-treatment on the expression of endogenous opioids and opioid receptors in the CNS and in the colon. Here, OPRD1 is linked to colitis.