Genetic Control of F Cells in Human Adults

Hb F levels were determined on samples from 750 normal blood donors. Six individuals (0.8 %) had Hb F levels in excess of 1.1 %, the upper end of the continuous distribution. Eight individuals at the upper end and 7 individuals at the lower end of the range were selected for family studies. These studies revealed that the control of Hb F levels in adults, as judged by the more sensitive F-cell technique, has a major genetic component. Structural analysis of the Hb F in several cases demonstrated that both Gγ and Aγ chains were present, but in variable proportions. These results are discussed in light of current concepts of adult F-cell production.