Activating and inhibitory killer immunoglobulin-like receptors (KIR) in haploidentical haemopoietic stem cell transplantation to cure high-risk leukaemias

Authors

  • A. Moretta,

    Corresponding author
    1. Department of Experimental Medicine and Center of Excellence for Biomedical Research, University of Genova,
    • A. Moretta, Head Molecular Immunology Laboratories, Dipartimento di Medicina Sperimentale, Sezione di Istologia, School of Medicine, University of Genova, Via G.B. Marsano 10, 16132 Genova, Italy.
      E-mail: alemoret@unige.it

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  • D. Pende,

    1. Istituto Nazionale per la Ricerca sul Cancro, Genova,
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  • F. Locatelli,

    1. Pediatric Hematology/Oncology, University of Pavia, IRCCS Foundation, Policlinico San Matteo, Pavia, and
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  • L. Moretta

    1. Department of Experimental Medicine and Center of Excellence for Biomedical Research, University of Genova,
    2. Giannina Gaslini Institute, Genova-Quarto, Italy
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Summary

A number of experimental studies have shown that natural killer (NK) cells can eliminate cancer cells and the mechanisms involved in this effect have been uncovered during the last two decades. Clinical data from haploidentical haematopoietic stem cell transplantation (haplo-HSCT) revealed that NK cells were responsible for remarkably favourable effects in both adult and paediatric high-risk leukaemias. NK receptors specific for major histocompatibility complex (MHC) class I molecules, including killer immunoglobulin (Ig)-like receptors (KIR) and CD94/NKG2A, play a major role in the anti-leukaemia effect (mediating either inhibitory or activating signals). Haplo- HSCT requires a heavy conditioning regimen for the patient and the use of large numbers of T cell-depleted HSC to be grafted. After transplantation, natural killer cells develop from HSC shortly after engraftment and may include ‘alloreactive’ NK cells that kill leukaemic cells and prevent graft-versus-host disease (GvHD). Alloreactive NK cells are characterized by the expression of KIR that are not engaged by any of the human leucocyte antigen (HLA) class I alleles expressed by the patient. Their generation is dependent upon the existence of a KIR/HLA class I mismatch between donor and recipient. Novel important information on the function and specificity of different KIR has been obtained recently by the analysis of donor-derived alloreactive NK cells in a cohort of paediatric patients given haplo-HSCT to cure acute, high-risk leukaemias.

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