CD200R1 and rectal cancer: In humans, CD200R1 is mainly expressed on myeloid-derived and lymphoid-derived immune competent cells (32) and the interaction with its ligand CD200R1 was reported to promote relapse of rectal cancer (33), to be involved in HCC progression (34) and high expression of CD200R1 was associated with poor prognosis in non-small cell lung cancer (35).