Erythrocytic Chalone, a Tissue‐specific Inhibitor of Cell Proliferation in the Erythron

Control of the rate of cellular proliferation in the erythron seems to be mediated by a tissue‐specific mitotic inhibitor, termed the erythrocytic chalone. the function of this substance seems to be to prevent excessive proliferation of the erythrocyte precursor cells by means of a negative feedback and in terms of peripheral cell numbers. The erythrocytic chalone is present in mature erythrocytes, from which it can be extracted by incubation in a chemically defined medium. It is also present in fresh normal serum and it is possible that in physiological conditions the factor is continuously liberated from mature erythrocytes into the surrounding plasma. In the rat, in an artificially induced polycythaemia the concentration of the chalone in the serum is increased and this increment appears to be the sole cause of the enhanced inhibitory action of polycythaemic serum on the proliferation of the bone marrow cells in vitro. The mode of action of the erythrocytic chalone seems to be to prevent the erythrocyte precursor cells from entering the generative cell cycle; the chalone thus regulates the production of erythrocytes by changing the ‘proliferation efficiency’ in the erythron. So far, nothing is known about the chemical nature of the erythrocytic chalone. However, in gel filtration it is eluted in the same zone as the granulocytic chalone, its molecular weight thus being about 2000‐4000.