Comparison of response to stem cell differentiation signals between normal and autoimmune mouse strains

Normal DBA/2 and autoimmune NZB mice were studied with regard to signals eliciting differentiation and division of bone marrow stem cells. Irradiated (NZB X DBA/2)F1 mice were repopulated with various combinations of T-depleted bone marrow from NZB and DBA/2 mice. In response to the repopulation signal of irradiation, recipients of autoimmune NZB marrow initially demonstrated expansion of LY-5+ lymphoid and hemopoietic cells, particularly of the B cell lineage. The greater the proportion of NZB marrow, the higher the percentage of lymphoid cells observed 2 wk post-repopulation. B cells (ThB-positive cells) were increased in disproportionate numbers in recipients of NZB marrow, even those that had received as little as 20% NZB bone marrow cells. However, by 2 mo, the initially observed increase in lymphoid cells in recipients of NZB marrow was no longer observed. Up to 6 mo post-repopulation, cytogenetic analysis revealed that irradiated recipients were repopulated in the same proportion of DBA/2: NZB as was in the injected marrow. Endogenous colony formation assays indicated that recipients of 100% NZB, 80% NZB, and 20% NZB marrow all had greater numbers of splenic endogenous colonies than did recipients of DBA/2 marrow alone. These studies indicated that autoimmune NZB marrow repopulated irradiated mice in the proportion in which it was injected, but there was a disproportionate early increase in cells of the B lineage as well as a disproportionate increase in splenic colony formation.