Bone marrow homing and engraftment defects of human hematopoietic stem and progenitor cells

Homing of hematopoietic stem cells (HSC) to their microenvironment niches in the bone marrow is a complex process with a critical role in repopulation of the bone marrow after transplantation. This active process allows for migration of HSC from peripheral blood and their successful anchoring in bone marrow before proliferation. The process of engraftment starts with the onset of proliferation and must, therefore, be functionally dissociated from the former process. In this overview, we analyze the characteristics of stem cells (SCs) with particular emphasis on their plasticity and ability to find their way home to the bone marrow. We also address the problem of graft failure which remains a significant contributor to morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). Within this context, we discuss non-malignant and malignant hematological disorders treated with reduced-intensity conditioning regimens or grafts from human leukocyte antigen (HLA)-mismatched donor

Occurrence of immune thrombocytopenic purpura in a patient with essential thrombocythemia: How the immune system can overcome a neoplastic clone

Our case highlights the possible coexistence of essential thrombocythemia (ET) and idiopathic thrombocytopenic purpura (ITP), two pathological entities with opposite clinical and laboratory manifestations. It also underlines how an autoimmune attack has been temporarily able to overcome a neoplastic clone

Clinical course and features of persistent polyclonal B-cell lymphocytosis with BCL-6 amplification during pregnancy

Background: Persistent polyclonal B-cell lymphocytosis is a rare nonmalignant disorder characterized by mild persistent lymphocyte proliferation with possible evolution to aggressive lymphoma. Its biology is not well known, but it is characterized by a specific immunophenotype with rearrangement of the BCL-2/IGH gene, whereas amplification of the BCL-6 gene has rarely been reported. Given the paucity of reports, it has been hypothesized that this disorder is associated with poor pregnancy outcomes. Case report: To our knowledge, only two successful pregnancies have been described in women with this condition. We report the third successful pregnancy in a patient with PPBL and the first with amplification of the BCL-6 gene. Conclusions: PPBL is still a poorly understood clinical condition with insufficient data to demonstrate an adverse effect on pregnancy. The role of BCL-6 dysregulation in the pathogenesis of PPBL and its prognostic significance are still unknown. Evolution into aggressive clonal lymphoproliferative disorders is possible and prolonged hematologic follow-up is warranted in patients with this rare clinical disorder

Chronic graft vs. host disease and hypogammaglobulinemia predict a lower immunological response to the BNT162b2 mRNA COVID-19 vaccine after allogeneic hematopoietic stem cell transplantation

Due to the high mortality rate of COVID-19, the assessment of BNT162b2 SARS-CoV-2 mRNA vaccine (Pfizer-BioNTech) efficacy in allogeneic hematopoietic stem cell transplant (HSCT) recipients is mandatory