CD4+T-cell–dependent aberration of B-cell progenitor niche in cGVHD animals. B10.BR mice were transplanted with BM only or BM and T cells from B6 donor mice. A subgroup of BM plus T-cell animals received injections of anti-CD4 on days 5, 7, 12, and 14 posttransplantation (GK1.5, 0.5 mg/mouse). Tibiae and femurs for osteoblast analysis and BM were harvested on day 30. (A) Frequency of infiltrating CD4+ T cells in the BM on day 30. Combined data from 2 independent experiments. *P < .05 (Mann-Whitney U test); n = 11 for BM only and BM plus T cells, and n = 6 for BM+T (anti-CD4). (B) Frequency of osteoblasts isolated from tibiae and femurs (percentage of Ter119−CD31−CD51+cells in the CD45− gate) 30 days posttransplantation. Combined data from 2 independent experiments, *P < .05, **P < .01 (Mann-Whitney U test), N = 11 for BM only and BM+T cells, N = 6 for BM+T (anti-CD4). (C) Frequency determined from the total number of cells in the BM (top) and overall number (bottom) of donor derived pre-pro B (B220+CD43+CD19−IgM−), pro B (B220+CD43+CD19+IgM−), pre B (B220+CD43-CD19+IgM−) and immature B cells (B220+CD43-CD19+IgM+) isolated from the BM of transplanted mice. Combined data from 2 independent experiments are shown. ***P < .001 (Mann-Whitney U test); n = 8 for all groups. (D-E) Prrx-1+YFP+ mice on a B6 background were transplanted with BM only or BM and T cells from B10.BR donor mice, and representative flow cytometry plots (D) and frequency of Prrx-1 YFP+ perivascular cells isolated from tibiae and femurs in CD45-Ter119− gate at day 30 after the transplantation (E) are shown. Combined data from 3 independent experiments are shown. **P < .01 (Mann-Whitney U test); n = 5 for BM only and n = 7 for BM plus T cells. (F) Overall number of donor-derived CLP, pre-pro–B (B220+CD43+CD19−IgM−), pro-B (B220+CD43+CD19+IgM−), pre-B (B220+CD43−CD19+IgM−), and immature B cells (B220+CD43−CD19+IgM+) isolated from the BM of transplanted mice. The BM plus T group received daily injections of either saline (black bars) or 1 μg/mouse mIL-7 (green bars) during the first 2 weeks posttransplantation. *P < .05 (Mann-Whitney U test); n = 5 for BM only, n = 3 for BM plus T cells (saline), and n = 4 for BM plus T cells (mIL-7). Bars represent standard error of the mean.