Two mechanisms may explain this protection: first, the CD200-CD200R pathway may help maintain immune homeostasis by curbing excessive inflammation, thereby preventing inadvertent tumor promotion; second, its cellular source is critical—our single-cell analysis indicates predominant endothelial expression of CD200, which may regulate immune cell trafficking and adhesion, thereby shaping the quality of anti-tumor immunity (62–64). Here, CD200R1 is linked to neoplasm.