In Vivo Activated CD103⁺CD4⁺ Regulatory T Cells Ameliorate Ongoing Chronic GVHD.

The α_Eβ₇ integrin CD103 is an excellent marker for identifying in vivo activated CD4⁺ regulatory T (Treg) cells. CD103⁻ naive Treg cells from donors are effective in prevention but ineffective in treatment of graft versus host disease (GVHD). It is unknown whether in vivo activated donor CD103⁺ Treg cells can effectively treat ongoing GVHD. We have recently reported a new chronic GVHD model, in which donor DBA/2 (H-2^d) spleen cells were transferred to the irradiated BALB/c (H-2^d) recipients. The recipients showed chronic GVHD-like syndrome with high-levels of serum autoantibodies, proteinuria, and hair-loss, and the disease induction required both donor CD4⁺ T and B cells in a cell dose dependent manner (Blood, 2006). In the current studies, we observed that the percentage of CD103⁺ cells among donor CD4⁺ T cells in the recipients without disease was up to 45% and was more than two fold higher than that of the recipients with disease. The CD103⁺CD4⁺ T cells were more than 97% FoxP3⁺, which was similar to natural CD25^hi Treg cells, but the former expressed markedly higher levels of CCR5 as compared to the latter. The CD103⁺ Treg cells showed markedly stronger suppression capacity as compared to freshly isolated as well as in vitro anti-CD3-activated CD25^hi natural Treg cells. When injected into ongoing chronic GVHD recipients with severe proteinuria, CD103⁺ Treg cells (1x10⁶) reversed proteinuria and tissue damages in 92% (11/12) of the recipients, and the recipients survived for more than 100 days. In contrast, the in vitro activated natural Treg cells reversed disease in only 25% (2/8) of the recipients, and the freshly isolated CD25^hi natural Treg cells reversed none (0/12), and the treated recipients died within 45 days, which was similar to control PBS treated recipients. Furthermore, we found that infusion of the CD103⁺ Treg cells significantly reduced CD138⁺ antibody-secreting plasma cells in spleen and reduced serum levels of autoantibodies; and that infusion of the CD103⁺ Treg cells also significantly reduced CD44^loCD62L^hiSCA-1^hi post-mitotic CD4⁺ T memory stem cells in spleen as well as pathogenic IFN-γ⁺CD4⁺ T cells in liver and nephritogenic IFN-γ⁺IL-10⁺CD4⁺ T cells in kidney tissues. Our results indicate that, different from CD103⁻ naive natural Treg cells that prevent GVHD via suppressing donor T cell activation and expansion, CD103⁺ Treg cells ameliorate ongoing chronic GVHD via reducing activated pathogenic T and B cells.