Jeffrey M. Lipton

An intrinsic progenitor defect in Diamond‐Blackfan anaemia

Summary. To determine whether the erythropoietin (epo) insensitivity of erythroid progenitor differentiation in congenital pure red cell aplasia or Diamond‐Blackfan anaemia is intrinsic to the progenitor itself or is due to defective accessory cell function or active suppression, progenitors from normals and two patients (one steroid resistant and one spontaneously remitting), separated from all known accessory cells using sequential negative selection techniques (adherence, E‐rosetting, and direct and indirect immune‐panning), were studied. Initially, we evaluated three patients with DBA using unfractionated bone marrow mononuclear cells. Progenitors from two steroid non‐responsive patients showed insensitivity to crude epo (c‐epo) while one steroid responsive patient demonstrated normal in vitro sensitivity to c‐epo. When recombinant epo (r‐epo) was used in place of c‐epo, the two steroid non‐responders continued to demonstrate in vitro progenitor epo insensitivity. However, sensitivity of progenitors from the steroid responder, which was normal in the presence of c‐epo, became abnormal when recombinant epo (r‐epo) was substituted. Thus, using unfractionated bone marrow, the abnormal response to epo of progenitors from some patients with DBA appears to be obscured by stimulating factors termed erythroid burst‐promoting activity (BPA) which are present in c‐epo. Using fractionated highly enriched progenitors, from normals and a steroid responsive patient a final 3–10‐fold enrichment of progenitors was achieved, but no such enrichment was seen when marrow from a steroid resistant patient was cultured. The epo sensitivities of normal and of patient erythroid progenitors were similar. However, at sub‐optimal epo concentrations in both patients CFU‐E responsiveness to crude BPA was abnormal compared to the three controls. We conclude from these studies that in DBA: (a) the failure of erythropoiesis is due to an intrinsic progenitor defect; (b) this defect involves progenitor insensitivity to factors in addition to erythropoietin; and (c) there exists a spectrum of disease reflected in the degree of the in vitro abnormality observed.

Lack of effect of corticosteroids in W/Wv and Sl/Sld mice: These strains are not a model for steroid-responsive Diamond-Blackfan anemia

Abstract: W/Wv and Sl/Sld mice with macrocytic anemias are a potential model for human inherited pure red cell anemia, called Diamond‐Blackfan anemia (DBA). The W mutation involves the gene for c‐kit, and the SI mutation the gene for the kit ligand, called mast cell growth factor, steel factor, or stem cell factor. Since many children with DBA respond to treatment with corticosteroids, we administered steroids to these genetically anemic mice, to determine whether they might provide a model for the human disease. There was no improvement in the murine anemia, consistent with other evidence suggesting that mutations in kit or steel may not be involved in Diamond‐Blackfan anemia.

Disparate lympho-erythroid donor to recipient chimaerism in a β°-thalassaemia bone marrow transplant recipient with red cell indices indicative of apparent full engraftment

A 4‐year‐old girl with transfusion‐dependent β°‐thalassaemia received an HLA‐identical bone marrow transplant (BMT) from her β°‐thalassaemia trait sister. Prior to BMT, chromosomal analysis revealed the recipient to have 46,XX,9qh+, a polymorphic variant of the heterochromatin region of chromosome 9, which her donor did not have. Within 1 month post‐BMT, 89% of nucleated bone marrow cells were of donor origin. One year later, donor engraftment had decreased to 44% and 34% in nucleated bone marrow cells and blood lymphocytes, respectively. By 2 years, donor lymphocyte engraftment fell to 5%, raising concern of possible graft rejection. To examine erythroid chimaerism, globin synthesis by individual erythroid progenitor cell derived colonies (BFU‐E) was analysed. On days 1000 and 1130 post‐BMT, 79% and 77% of colonies, respectively, synthesized β‐globin and therefore were of donor origin.

Chapter 8 – Bone Marrow Failure

This chapter describes the causes, clinical manifestations, diagnosis and treatment of various types of both acquired and inherited bone marrow failure syndromes.