WT pDC limit the GVHD activity of donor T cells while enhancing donor T-cell proliferation. (A) Survival of mice that received 3 × 103 FACS-sorted HSCs + 1 × 106 MACS-enriched B6 splenic T cells with or without 5 × 104 FACS-purified pDCs from either WT or IDO1−/− mice in the B6→BA.B10 transplant model (*P = .002 comparing WT pDC and IDO1−/− pDC recipient groups). (B) GVHD scores for these groups (**P < .0006 comparing WT pDC and IDO1−/− pDC recipient groups). Data are means ± SEM from 4 replicate experiments with average 6 mice per group. (C) B10.BR mice received 5 × 103 FACS-sorted B6 HSCs and 1 × 106 B6 (CD45.1+) T cells, with or without addition of 5 × 104 FACS-purified pre-pDCs from WT or IDO1−/− B6 donors. The experiment was performed 3 times with 2 to 3 mice per group, for a total n = 7 for the HSC + T group and n = 8 for the groups with added WT pDCs or IDO1−/− pDCs. T cells were CFSE labeled before transplant. Proliferation profiles for donor CD45.1+ CD4 and CD8 T cells recovered from recipient spleens on day 3.5 after transplant are shown for representative samples, with gates indicating the percentages of cells that remained undivided (right) or that were in divisions 1 to 6 (center) or later divisions (left). Bar graphs show the average percentage of undivided CD4 or CD8 T cells in the CFSE profile and the calculated proliferation indices. (D) Representative flow cytometry plots gated on donor CD4 T cells from recipient spleens on day 3.5 after transplant, with boxes indicating the CD25+ FoxP3+ T-reg population. (E) Comparisons of the absolute numbers of donor graft-derived CD8 and CD4 T cells and CD4+CD25+FoxP3+ T-regs present in recipient spleens on day 3.5 after transplant.
