KLRC2 and chronic graft versus host disease: Among all alloSCT patients and among patients receiving an HLA-mismatched graft, patients with severe aGvHD or extended chronic GvHD (cGvHD) show a significantly lower ratio of CD94/NKG2C to CD94/NKG2A during the whole observation period post-alloSCT compared to patients with no or only mild acute or chronic GvHD.