Natural killer (NK) cell function is regulated by inhibitory receptors, such as the family of killer immunoglobulin-like receptors (KIRs) and the NKG2A/CD94 heterodimer. These receptors recognize cognate HLA class I molecules on potential target cells, and recent studies imply that an HLA-B dimorphism at position −21 in the gene segment encoding the leader peptide dictates whether NK cell regulation primarily relies on the KIRs or the NKG2A/CD94 receptor. The impact of this HLA-B dimorphism on NK cell–mediated destruction of leukemic cells or on the course of leukemia is largely unknown. In a first part of this study, we compared functions of NK cells in subjects carrying HLA-B −21M or 21T using interleukin-2 (IL-2)–activated NK cells and leukemic cells from patients with acute myeloid leukemia (AML). Subjects carrying HLA-B −21M harbored better-educated NKG2A+ NK cells and displayed superior capacity to degranulate lytic granules against KIR ligand-matched primary leukemic blasts. Second, we aimed to define the potential impact of HLA-B −21 variation on the course of AML in a phase 4 trial in which patients received IL-2–based immunotherapy. In keeping with the hypothesis that 21M may be associated with improved NK cell functionality, we observed superior leukemia-free survival and overall survival in −21M patients than in −21T patients during IL-2–based immunotherapy. We propose that genetic variation at HLA-B −21 may determine the antileukemic efficacy of activated NK cells and the clinical benefit of NK cell–activating immunotherapy.

May-Hegglin anomaly (MHA) is an autosomal dominant disorder, characterized by a variable degree of thrombocytopaenia, large platelets and inclusion bodies in white blood cells. Bleeding manifestations are generally mild, but severe bleeding episodes have been reported. This is a systematic review of literature for MHA during pregnancy. The review revealed 26 articles (25 case reports and one case series) including 75 pregnancies (five twin pregnancies) in 40 women. In 11 women, first presentation was incidental thrombocytopaenia during routine antenatal blood test. Of these, five women were misdiagnosed as idiopathic thrombocytopenic purpura (ITP), including three who underwent splenectomy for resistant ITP. Postpartum haemorrhage (PPH) and bleeding after miscarriage were presenting symptoms in two women. Antiplatelet antibody was found in three pregnancies. Only one of them required intervention with intravenous immunoglobulin (IVIG) to prevent neonatal alloimmune thrombocytopaenia. PPH was reported in four pregnancies; three were primary PPH, of which one had blood transfusion, one had platelet and cryoprecipitate transfusion and the third was managed conservatively. There was one secondary PPH that was treated conservatively. Neonatal outcome included 78 live neonates and two intrauterine fetal deaths. Thirty-four neonates had thrombocytopaenia and subsequently were diagnosed with MHA, three of them required platelet transfusion prophylactically as they developed very low platelet counts and one neonate with platelet count of 29 × 10 cells/l and received IVIG, as the mother had a positive antiplatelet antibody during pregnancy. No obvious bleeding complications were reported among the neonates. MHA can present challenges during pregnancy and be associated with adverse maternal and neonatal outcome because of bleeding complications. Joint management by obstetrician and haematologists is required to minimize these risks.

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