KLRK1 and Ewing sarcoma: Based on our current results demonstrating non-elevated soluble MICA levels in plasma of Ewing sarcoma patients (as compared to age-comparable healthy controls) as well as our previous observation of intact NKG2D expression on natural killer cells of these patients [20], we do not consider NKG2D ligand shedding a relevant immune escape mechanism in patients with this tumour.