In the TME, CD200 is mainly expressed in some types of cancer cells, activated immune cells such as T cells, and endothelial cells, while CD200R is predominantly expressed in myeloid cells such as TAMs, MDSCs and DCs. Tregs also express significant levels of CD200R. Interactions among these cell types in TME are likely to determine the outcome of the tumor associated inflammation and immune response, and subsequently affect tumor growth and metastasis.