Peripheral immunological tolerance is critical to prevent autoimmunity but detail of the mechanism has not been exactly understood. The perpose of this study is to determine whether peripheral tolerance exists to desmoglein 3 (Dsg3), a pemphigus autoantigen, and to clarify its mechanisms in mice. To achieve this, Dsg3-/- thymus was transplanted to nude mice that lack thymus, and followed by bone marrow transfer of Dsg3-specific TCR transgenic (Dsg3H1) mice. This experimental setting provides a unique condition where Dsg3 is not expressed in thymus, but in the peripheral organ, such as skin. While Dsg3H1 CD4+ T cells developed in thymus, they significantly decreased in ratio in periphery (spleen and skin-draining lymph node, n = 7). Furthermore, when peripheral Dsg3H1 T cells that developed in the absence of Dsg3 as in Dsg3H1-Dsg3-/- mice were adoptively transferred to WT mice that express Dsg3, DsgH1 T cells disappeared in the periphery on Day14. To characterize crucial cell subsets and molecules involved in this T cell elimination, various gene-engineered mice were used as recipients. The elimination of Dsg3H1 T cells was affected in MHC II-/- (n = 6), CCR7-/- mice (n = 9) and WT recipients reconstituted by MHC II-/- bone marrow (BM) cells (n = 12), but not affected in Aire-/-, Langerin-DTA and DT-injected Langerin-DTR mice, indicating that the T cell elimination requires BM-derived antigen presenting cells (APCs) in a CCR7 dependent manner. Moreover, under in vivo ablation of Foxp3+ cells (Treg) in DEREG mice with DT, Dsg3H1 T cells failed to be eliminated, and not only that vigorously expanded and induced T cell-mediated dermatitis (n = 8). The T cell elimination was restored when Treg were added back in DEREG mice. These findings indicate the existence of the peripheral tolerance to Dsg3 in mice and the essential role of Treg in in vivo deletion of autoreactive CD4+ T cells as a novel peripheral tolerance mechanism.

Regulatory T cell is essential for deletion of autoreactive CD4+ T cells to desmoglein 3 in peripheral tolerance