Age-dependent abnormalities of hematopoietic stem cells in (NZW x BXSB)F1 mice.

The (NZW x BXSB)F1 (W/BF1) mouse is known as an autoimmune-prone strain which develops lupus nephritis, thrombocytopenia due to platelet-specific autoantibodies, leukocytosis, and myocardial infarction. In this experiment, we investigated the age-dependent abnormalities of the hematopoietic stem cells (HSCs) and hematopoiesis in this mouse. White blood cell counts (especially Mac-1- or Gr-1-positive cells) in the peripheral blood of 12-week-old W/BF1 mice increased in comparison with those of four-week-old W/BF1 or normal mice. To investigate whether the abnormal hematopoiesis can be attributed to the HSCs of W/BF1 mice, colony-forming unit in spleen (CFU-S) and colony-forming unit in culture (CFU-C) assays were performed. Day 12 CFU-S counts of 12-week-old W/BF1 mice significantly increased in comparison with those of four-week-old W/BF1 mice or normal mice. In the CFU-C assay, CFU-GEMM and CFU-GM counts in 12-week-old W/BF1 mice increased in comparison with those of four-week-old W/BF1 or control mice. The bone marrow cells (BMCs) from 12-week-old W/BF1 mice showed a high level of G-CSF and a low level of GM-CSF in mRNA expression. To examine the effect of HSCs from 12-week-old W/BF1 mice on the onset of autoimmune diseases and the abnormal hematopoiesis, T- and B-cell-depleted BMCs of four-week-old or 12-week-old W/BF1 mice were transplanted to C3H mice. Recipient C3H mice that had received the BMCs from 12-week-old W/BF1 mice showed an earlier onset of autoimmune diseases and a shorter survival rate than those that had received the BMCs from four-week-old W/BF1 mice. These data suggest that the HSCs from 12-week-old W/BF1 mice showing the symptoms of autoimmune diseases have the capacity to induce autoimmune diseases earlier than the HSCs from four-week-old W/BF1 mice.