Hemopoiesis in mouse heterozygous for the W trait. Difference in postirradiation recovery related to the defect in formation of transient endogenous spleen colonies.

The hemopoietic regeneration following midlethal irradiation in Wv/+ mice had similarly biphasic kinetics as in their hematologically normal +/+ littermates. The first abortive phase of regeneration was either severely reduced (formation of transient endogenous spleen colonies, reticulocyte count, granulocyte count) or absent (spleen and femur cellularity, platelet count, PCV) in Wv/+ mice, when compared to +/+ mice. The second phase leading to permanent recovery of hemopoiesis was in Wv/+ mice delayed in time. Moreover, although to a lesser extent the values of spleen and femur cellularity, PCV and platelet count were decreased in Wv/+ mice. Postirradiation bleeding, which stimulated particularly the 1st phase of regeneration both in Wv/+ and +/+ mice did not lead to the minimization of differences between above two genotypes. It is suggested that the observed differences in the abortive regeneration between Wv/+ and +/+ mice are primarily dependent on the presence in Wv/+ mice of selective defect of transient endogenous colony forming units (TE-CFUs). Moreover, it is possible that the differences in the second phase of regeneration leading to permanent recovery are secondarily dependent on the TE-CFUs defect, as most probably the TE-CFU is the step in stem cell differentiation to mature cells.