Fetal hemoglobin accumulation in vitro. Effect of adherent mononuclear cells.

In clonal cultures of erythroid burst-forming units (BFU-E) obtained from blood, the accumulation of fetal and adult hemoglobins (Hb F and Hb A) was measured by radioligand immunoassay. Inclusion of adherent mononuclear cells in the culture promoted a striking increase in the relative amount of Hb F in each of 44 experiments with 14 donors. In two-thirds of the instances, this was accounted for by a selective increase in the absolute amount of Hb F. The differential effect on Hb F and Hb A accumulation was achieved without altering the maturity of the erythroid cells, their mean hemoglobin content, or the asynchrony of the production of the two hemoglobins. Virtually all bursts produced Hb F, and the population of BFU-E as a whole, rather than a selected subset, appeared to be the target of adherent cell action. When the adherent cells were excluded from the culture input, the base-line value of Hb F was reproducible for each donor over a period of several months, and correlated with the number of in vivo circulating F cells.