Erythroid-committed progenitors and spleen colony-forming cells in adult thymus-deprived mice.

The effect of thymus deprivation on spleen colony-forming unit (CFU-s), the erythroid repopulating ability (ERA) of bone marrow cells, erythropoietin-responsive cells (ERC) and the erythroid colony-forming unit (CFU-e) was investigated in adult mice. Female CBA mice, thymectomized at the age of 6 weeks, were used for the experiments at 3 to 5 weeks later (Tx). Thymectomized, lethally irradiated and bone marrow cell-reconstituted mice (TIR) were used 2 months after reconstitution. A decrease of ERA was found if Tx animals were used as recipients of normal or Tx bone marrow cells. Estimated values of ERC and number of CFU-e-derived colonies in the bone marrow and spleen in response to 3 units of erythropoietin (Ep) were lower in Tx than in control polycythaemic mice. In TIR animals, a lower number of femoral CFU-s was found, but the ERA and ERC values were not affected. However, in response to 3 units of Ep, the number of CFU-e-derived colonies differed in the bone marrow of TIR animals as compared to the values found in normal, reconstituted mice.