α, β, and γ globin chain synthesis in bone marrow and peripheral blood reticulocytes were studied in two patients with thalassemia major, two with thalassemia intermedia, one with thalassemia minor, one with Hb H disease, and one with homozygous βδ-thalassemia. Nine nonthalassemic patients served as controls. In thalassemia major, a marked imbalance of α- to β-chain synthesis was found in the bone marrow as well as in reticulocytes. The imbalance, however, was slightly more evident in the latter. In the patients with thalassemia intermedia and minor the α- to β-globin chain ratios in the reticulocytes were of the same order of magnitude, despite the marked clinical differences between thalassemia intermedia and minor. A balanced synthesis was found in the bone marrow of the patient with thalassemia minor. The bone marrow globin synthesis in thalassemia intermedia was not studied. Contrary to that in Hb H disease and βδ-thalassemia, the imbalance was more apparent in the bone marrow. In the latter, no evidence for imbalance was detected in the reticulocytes. These results point out the need for further studies on globin chain synthesis in the bone marrow and reticulocytes of patients With the various thalassemia syndromes and the effect of the free globin chain pool on those results.

Human fetal liver maintained in tissue culture has been examined as a model system for studying the factors involved in the switch from fetal to adult haemoglobin production. In erythropoietin-treated cultures alpha-, beta- and gamma-chain synthesis remains active for up to 12 days. Globin-chain synthesis is balanced and the alpha/beta + gamma-chain production ratio remains constant up to about 8 days; in longer cultures gamma-chain production declines before that of beta chains. It is concluded that the system may be useful for examining factors involved in the switch from gamma- to beta-chain production provided that these are acting on cells already committed to the erythroid compartment.

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