Figure 2.

Treg treatment induces low but persistent levels of hematopoietic chimerism without the need for recipient irradiation. (a) Groups of B6 mice received fully mismatched BALB/c BM cells (20 × 10⁶), combined costimulation blockade with CTLA4Ig and MR1, and either pre-treatment with 3-Gy TBI (3 Gy, 6/6 chimeras), polyclonal recipient-type Tregs with short-term rapymycin (5/5 chimeras) or rapaymycin alone (0/5 chimeras). Long-term donor (H-2D^d) chimerism among leukocytes of the myeloid (Mac1⁺) lineage was assessed by flow-cytometric analysis of peripheral blood at multiple time-points. (B, C) Multilineage chimerism in lymphoid tissue (BM, spleen) was assessed at the end of follow-up (~7 months post-BMT). (B) Mean levels of B-cell and myloid chimerism within BM are shown for irradiated BMT recipients (3 Gy, open bars, n = 6), Treg-treated BMT recipients (0-Gy Tregs, filled bars, n = 4) and the unirradiated control group (0-Gy control, shaded bars, n = 5). (C) Mean levels of CD4 T-cell, CD8 T-cell and B-cell chimerism among splenocytes are shown for irradiated BMT recipients (3 Gy, open bars, n = 6), Treg-treated BMT recipients (0-Gy Tregs, filled bars, n = 4) and the unirradiated control group (0-Gy control, shaded bars, n = 5). ^***p < 0.0005, ^**p < 0.005 and ^*p < 0.05 (Student’s t-test). Error bars indicate standard deviation. Data represent multiple experiments.