There are very few human MAIT cells in cord blood. Ben Youssef et al. show that they slowly expand during childhood and point to a critical role of the TCRαβ repertoire in determining their unique ability to recognize MR1-restricted microbial antigens.

Busulfan (BU) dose adjustment following therapeutic drug monitoring contributes to better outcome of hematopoietic stem cell transplantation (HSCT). Further improvement could be achieved through genotype-guided BU dose adjustments. To investigate this aspect, polymorphism within glutathione S transferase genes were assessed. Particularly, promoter haplotypes of the glutathione S transferase A1 (GSTA1) were evaluated in vitro, with reporter gene assays and clinically, in a pediatric multi-center study (N =138) through association with BU pharmacokinetics (PK) and clinical outcomes. Promoter activity significantly differed between the GSTA1

Parenteral nutrition (PN) is the treatment of choice for nutritional support of patients undergoing allo-SCT following myeloablative conditioning (MAC). Here we prospectively assessed the outcomes of early enteral nutrition (EN) in a paediatric cohort. From 2003 to 2010, all 65 consecutive children undergoing MAC allo-SCT at our referral centre began EN the day after transplantation. Post-transplant and nutritional outcomes of patients receiving only EN (EN group, n ¼ 50) were compared with those of patients requiring additional PN (EN-PN group, n ¼ 15). In the EN group time to platelet recovery (P ¼ 0.01) and length of hospitalisation (Po0.001) were shorter, while in the EN-PN group the proportion of unrelated donors (P ¼ 0.02) and the frequency of severe acute GVHD (aGVHD; P ¼ 0.004) were higher. All patients were alive at day 100. PN was started 14 days after transplant because of poor digestive tolerance to EN or severe gut aGVHD. The body mass index Z-score in the EN-PN group decreased from transplant to discharge (P ¼ 0.02). In only 23% of cases was PN required for severely ill patients. Our results suggest that EN might be considered to be an option for nutritional support in children undergoing MAC allo-SCT, while PN should be used only as a rescue option, possibly in combination with EN.

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In these two short reports, the authors approach the issue of whether hydroxyurea (HU) use in young males has major irreversible effects on sperm production. Joseph et al analyzed and compared sperm parameters in male patients with sickle cell disease (SCD) who were exposed or not exposed to HU before puberty. They report semen abnormalities in all patients but no differences between groups. Independently, Gille et al provide evidence for the lack of in vivo HU-related decreases in the spermatogonial pool in biopsy specimens from young males with SCD but evidence for a negative effect of SCD itself. Together, these reports suggest that the use of HU in young males does not adversely affect fertility.

Summary Despite major therapeutic improvements, children with relapsed/refractory Acute Myeloid Leukaemia still have poor outcomes and overall survival does not exceed 40%. New treatments are required to improve their outcome; Gemtuzumab ozogamicin (GO), an anti‐CD33 immunoconjugate antibody, is a potent cytotoxic agent whose efficacy has been demonstrated mainly in adults. The main objective of this retrospective multicentre study was to assess the outcome of children treated, between February 2008 and August 2019, with GO at a single 4.5 mg/m2 dose, in combination with Fludarabine, Cytarabine and antssshracyclines, in context of a first relapse (n = 26) or refractory disease (n = 3). The remission rate was 83% (24/29 children) and 20 children (69%) were allografted. With a median follow‐up of 1.2 years (range: 0.1–8), the overall survival was 49% (CI95% = 33; 72). Most common adverse event was febrile neutropenia with microbiological identification in 55% of cases. Veno‐occlusive disease occurred in 6 patients (21%), of which 5 subvened after bone marrow transplantation, and resolved within 2–32 days (median 10.5 days). Administration of GO in combination with FLA‐anthracyclines chemotherapy appears to be a good reinduction regimen for relapsed or refractory AML with a good safety profile. These results warrant larger prospective study.

BackgroundMucosal-associated invariant T (MAIT) cells are semi-invariant T cells that recognize microbial antigens presented by the highly conserved MR1 molecule. MAIT cells are predominantly localized in the liver and barrier tissues and are potent effectors of antimicrobial defense. MAIT cells are very few at birth and accumulate gradually over a period of about 6 years during the infancy. The cytotoxic potential of MAIT cells, as well as their newly described regulatory and tissue repair functions, open the possibility of exploiting their properties in adoptive therapy. A prerequisite for their use as ‘universal’ cells would be a lack of alloreactive potential, which remains to be demonstrated.MethodsWe used ex vivo, in vitro and in vivo models to determine if human MAIT cells contribute to allogeneic responses.ResultsWe show that recovery of MAIT cells after allogeneic hematopoietic stem cell transplantation recapitulates their slow physiological expansion in early childhood, independent of recovery of non-MAIT T cells. In vitro, signals provided by allogeneic cells and cytokines do not induce sustained MAIT cell proliferation. In vivo, human MAIT cells do not expand nor accumulate in tissues in a model of T-cell-mediated xenogeneic graft-versus-host disease in immunodeficient mice.ConclusionsAltogether, these results provide evidence that MAIT cells are devoid of alloreactive potential and pave the way for harnessing their translational potential in universal adoptive therapy overcoming barriers of HLA disparity.Trial registration numberClinicalTrials.gov number NCT02403089.

Hermansky-Pudlak syndrome (HPS) was first described in 1959 in two patients with oculocutaneous albinism (OCA), prolonged bleeding, and pigmented macrophages in the bone marrow. To date, 11 HPS subtypes are reported and associated with 11 causative genes (Huizing et al., 2020; Pennamen et al., 2020). HPS genes encode subunits of BLOC complexes (Biogenesis of Lysosome-related Organelle Complexes), and pathogenic variants of these genes induce abnormal biogenesis of lysosome-like organelles, such as melanosomes