"HLA-A1 allele frequencies were overrepresented and HLA-A2 allele frequencies were underrepresented in cases of EBV + PTLD compared with EBV - PTLD after SOT. EBV + PTLDs in HLA-A1 carriers developed primarily in already EBV-seropositive recipients which suggests an impaired immunological control of the latent EBV infection in this subgroup."xsd:string