Effect of AAT on donor cell subpopulations. (A) Increase in the proportion of DCs in spleens of AAT-treated (AAT) and albumin-treated (controls) donors. Shown are spleen cells labeled for CD11c⁺CD205⁺CD8⁺ (left panels), and for MHC class II⁺CD205⁺CD86⁺ (right panels); data on all mice are summarized in the graph. (B) Treatment of CD11c-DTR mice expressing the DT receptor with DT or PBS (control). Bone marrow and spleen cells were collected and stained for CD11c. Following 2 injections of DT, CD11c-expressing cells were 80% to 90% depleted (see “Materials and methods”). (C) Survival of C3H.SW (H 2^bc) recipients of marrow plus spleen cells from C57BL/6 [H-2b] donors that had been treated with AAT (AAT) only or treated with AAT and also injected with DT. Recipients of DC-depleted donor cells had greater weight loss and higher GVHD scores (lower panels) than mice transplanted from donors not injected with DT (n = 7, each arm). (D) Treatment of donor mice transgenic for CD11c DTR with DT also significantly reduced the proportion of CD4⁺CD25⁺FoxP3⁺ Tregs.