CTLA4 and acute lymphoblastic leukemia: In summary, the CTLA-4 +49 GG and the haplotype ACGG/ACGG reduced the overall survival in ALL after allo-HSCT from the related HLA-haplotype-mismatched donor, knowledge of the CTLA-4 polymorphism and haplotype may provide useful information for donor selection and individual application of immunosuppressive agents and immunotherapy.