Detection of a diffusible factor controlling the synthesis of a single hemoglobin chain in mice

The synthesis of hemoglobin alpha-chains was investigated in splenic colonies derived from syngenic colony-forming units injected in lethally irradiated C3H mice. Whereas normal adult mice of this strain synthesize two structurally distinct alpha-chains, the "alphaC57" and the "alpha NB", chains, it was found that erythrocytes from splenic colonies of irradiated recipient mice contained no alpha chain of the C57 type. Daily injection of serum from adult C3H mice into irradiated recipient mice of the same strain stimulates the synthesis of alphaC57 chain, whereas the injection of serum of lethally irradiated mice, drawn 8 days after irradiation, does not. It is concluded that the serum of adult C3H mice contains one or several factors that are responsible for the differential activation of the synthesis of the alphaC57 globin chain. This factor is shown to be associated exclusively with a high molecular weight fraction of serum.