No abstract

Hemoglobin synthesis in a 34-year-old man of Laotian ancestry with Hb E/β°-thalassemia was studied. Hemoglobin electrophoresis exhibited only Hb F and Hb E. Reticulocytes and bone marrow cells showed no Hb A synthesis. The proportion of Hb F increased (from 14 to 50%) with the density of RBCs fractionated on a discontinuous gradient of Stractan. Reticulocytes were also heterogeneous with regard to their density and their Hb F synthesis: the proportion of Hb F synthesis increased with their density. Fractionation of bone marrow cells by density on a discontinuous gradient of Stractan provided populations of cells at different stages of maturation, the more mature having the greater density. Study of hemoglobin synthesis in bone marrow cells indicated that the proportion of γ-chains synthesized increased and the pool of free α-chains decreased with erythroblast maturation; in contrast, the proportion of βE-chains compared to α-chain synthesis remained constantly low. These results provide evidence that the increased amount of Hb F found in the blood of the patient was mostly due to the positive selection, in bone marrow and in peripheral blood, of cells containing Hb F. In contrast, colonies of early erythroid precursors derived from the blood of the patient exhibited an enormous reactivation of Hb F synthesis in culture. The low proportion of βE-chain synthesis (about 30% of α-chain synthesis) remained unchanged during the erythroid maturation of most immature erythroblasts to reticulocytes. The combination of two thalassemic alleles, one totally deficient (β°) the other partially deficient (βE), can explain the clinical severity of the association β⁰-thalassemia/Hb E.

In the present work we have developed an affinity chromatography system, using haptoglobin bound covalently to Sepharose 4B, to purify hemoglobin from soluble non‐heme proteins. Sepharosehaptoglobin specifically binds hemoglobin. It exhibits the same characteristics in its interactions with hemoglobin and α or β hemoglobin chains as does haptoglobin in solution. Globin chains can be eluted from the Sepharose‐haptoglobin after removal of the heme. This method has allowed accurate measurements of globin‐chain synthesis in blood and bone marrow samples and in culture of early erythroid precursors.