CD200 and neoplasm: To see if this inhibitory pathway contributed to immune evasion by the dormant tumor cells, we used shRNA to knock-down expression of CD200 in D2A1 tumor cells (Figure 6C) and observed fewer dormant lesions when these cells were injected into Tgfbr2MyeKO mice (Figure 6D), consistent with a role for CD200 in dormant tumor cell resistance to immune effector function.