CD200R1 and osteosarcoma: The expression of immune checkpoints LAG3, NRP1, CD40LG, C10orf54, CD86, CD48, CD274, HAVCR2, CD27, CTLA4, CD200R1, LAIR1, LGALS9, CD28, and PDCD1LG2 was significantly higher in the low-risk group than in the high-risk group, and it was previously confirmed in the literature that LAG3 [54], CD86 [55], HAVCR2 [56], CD27 [57], LAIR1 [58], and PDCD1LG2 [56] checkpoints play important roles in osteosarcoma cell therapy.