Up-regulation of activating and inhibitory NKG2 receptors in allogeneic and autologous hematopoietic stem cell grafts.

Alessandra Picardi,Enzo Gallo,Mirella Marino,Patrizio Giacomini,Rocco Fraioli,Edoardo Pescarmona,Andrea Mengarelli,Roberta Cocco,Paolo De Fabritiis,Maria Concetta Petti,Elisa Tremante,Maria Benevolo

doi:10.1186/s13046-015-0213-y

Abstract

BackgroundHematopoietic Stem Cell Transplantation (HSCT) is known to induce the inhibitory immune receptor NKG2A on NK cells of donor origin. This occurs in allogeneic recipients, in both the haploidentical and HLA-matched settings.MethodsTo gain further insight, not only NKG2A, but also the activating receptors NKG2C and NKG2D were assessed by flow cytometry. Immunophenotyping was carried out not only on CD56+ but also on CD8+ lymphocytes from leukemia and lymphoma patients, receiving both HLA-matched (n = 7) and autologous (n = 5) HSCT grafts. Moreover, cognate NKG2 ligands (HLA-E, MICA, ULBP-1, ULBP-2 and ULBP-3) were assessed by immunohistochemistry in diagnostic biopsies from three autotransplanted patients, and at relapse in one case.ResultsAll the NKG2 receptors were simultaneously up-regulated in all the allotransplanted patients on CD8+ and/or CD56+ cells between 30 and 90 days post-transplant, coinciding with, or following, allogeneic engraftment. Up-regulation was of lesser entity and restricted to CD8+ cells in the autotransplantation setting. The phenotypic expression ratio between activating and inhibitory NKG2 receptors was remarkably similar in all the patients, except two outliers (a long survivor and a short survivor) who surprisingly displayed a similar NKG2 activation immunophenotype. Tumor expression of 2 to 3 out of the 5 tested NKG2 ligands was observed in 3/3 diagnostic biopsies, and 3 ligands were up-regulated post-transplant in a patient.ConclusionsAltogether, these results are consistent with a dual (activation-inhibition) NK cell re-education mode, an innate-like T cell re-tuning, and a ligand:receptor interplay between the tumor and the immune system following HSCT including, most interestingly, the up-regulation of several activating NKG2 ligands. Turning the immune receptor balance toward activation on both T and NK cells of donor origin may complement ex vivo NK cell expansion/activation strategies in unmanipulated patients.Electronic supplementary materialThe online version of this article (doi:10.1186/s13046-015-0213-y) contains supplementary material, which is available to authorized users.

Highlights

Hematopoietic Stem Cell Transplantation (HSCT) is known to induce the inhibitory immune receptor NKG2A on Natural Killer (NK) cells of donor origin
Plasma was removed by washing, and 100 μl aliquots of packed blood cells were pre-incubated with 1 μg of murine Ig to saturate Fc receptors, and stained by simultaneous incubation for 30 min on ice with an FITC-conjugated mAb to either CD8 or CD56, and with PE-conjugated mAbs to NKG2A, NKG2C or NKG2D
Up-regulation of NKG2A, NKG2C and NKG2D in CD8+ T lymphocytes and CD56+ NK cells from allotransplanted patients Blood was obtained before and after transplant from the 7 patients listed in Table 1, and from their respective Human leukocyte antigens (HLA)-matched donors prior to donation

Summary

Introduction

Hematopoietic Stem Cell Transplantation (HSCT) is known to induce the inhibitory immune receptor NKG2A on NK cells of donor origin. This occurs in allogeneic recipients, in both the haploidentical and HLA-matched settings. Natural Killer (NK) cells bearing variable Killer Immunoglobulin-like Receptors (KIR) bind highly polymorphic class I Human Leukocyte Antigens (HLA-A, −B,−C), mount Graft versus Tumor (GvT) responses, and influence the outcome of patients with hematologic malignancies undergoing Hematopoietic Stem Cell Transplantation (HSCT). Even during hematopoietic self-replacement (autologous transplantation), approximately 60 % of the patients are expected to display the so-called ‘missing KIR’ phenotype, in that they express inhibitory KIRs that do not find a cognate HLA ligand on tumor cells. These NK cells may become cytokine-activated under appropriate conditions, positively affecting the outcome of hematopoietic malignancies and neuroblastoma [4, 5]

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