Involved in the recruitment or surface expression of the TYROBP receptor. Interacts with TYROBP. Highly expressed in monocytes, NK cells and a subset of NKT cells. Weakly expressed in granulocytes and B-cells (at protein level). Expressed in brain, lung, testis, thymus, intestine and uterus. Expressed in bone marrow derived-macrophage and dendritic cells and mast cells. Belongs to the CD200R family. May be expressed in adult splenic cells (PubMed:15187158), as the antibody used could not discriminate between CD200R1 and CD200R4. May be expressed in uterus at 12.5 dpc (at protein level) (PubMed:15274657), as the antibody used could not discriminate between CD200R1 and CD200R4. According to some authors (PubMed:15187158), CD200R4 is a receptor for the CD200/OX2 cell surface glycoprotein, but it was later found (PubMed:23602662) to miss key amino-acids for binding to CD200.