While it remains unclear if the dominant antigen in xenogeneic transplantation (or MHC mismatches in general) is directed against the specific mismatched HLA peptide or the antigens it presents, these studies highlight the possibility of using TCRβ diversity (i.e. Vβ spectratyping and/or TCRB sequencing) as a measurement of GVHD responses (64). The gene discussed is HLA-C; the disease is graft versus host disease.