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Blood, 15 April 2004, Vol. 103, No. 8, pp. 3122-3130. Prepublished online as a Blood First Edition Paper on December 4, 2003; DOI 10.1182/blood-2003-07-2500.
NEOPLASIA Down-regulation of HLA-A and HLA-Bw6, but not HLA-Bw4, allospecificities in leukemic cells: an escape mechanism from CTL and NK attack?From the HLA Laboratory, Academic Hospital VUB, Brussels, Belgium; the Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, The Netherlands; the Department of Immunohematology, Université Catholique de Louvain, Brussels, Belgium; the Department of Pathology, Henry Ford Hospital, Detroit, MI; and the Department of Immunology, Roswell Park Cancer Institute, Buffalo, NY.
Human leukocyte antigen (HLA) class I antigen defects may have a negative impact on the growing application of T-cellbased immunotherapeutic strategies for treatment of leukemia. Therefore in the present study, taking advantage of a large panel of HLA class I allelespecific human monoclonal antibodies, we have compared HLA class I antigen expression on leukemic cells with that on autologous and allogeneic normal cells. Down-regulation of HLA-A and/or -B allospecificities was present in the majority of the patients studied. However, down-regulation did not affect all HLA class I alleles uniformly, but was almost exclusively restricted to HLA-A allospecificities and to HLA-B allospecificities which belong to the HLA-Bw6 group. The latter allospecificities, at variance from those that belong to the HLA-Bw4 group, do not modulate the interactions of leukemic cells with natural killer (NK) cells. Therefore, our results suggest that the selective down-regulation of HLA-A and HLA-Bw6 allospecificities associated with HLA-Bw4 preservation provides leukemic cells with an escape mechanism not only from cytotoxic T lymphocytes (CTLs), but also from NK cells. As a result T-cellbased immunotherapeutic strategies for leukemia should utilize HLA-Bw4 alloantigens as restricting elements since a selective HLA-Bw4 allele loss would provide leukemic cells with an escape mechanism from CTLs, but would increase their susceptibility to NK cellmediated lysis. (Blood. 2004;103:3122-3130)
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