Aire-dependent thymic expression of desmoglein 3, the autoantigen in pemphigus vulgaris, and its role in T-Cell tolerance

In the mechanism of thymus-induced central tolerance, the transcription factor Aire has been demonstrated to promote the expression of a wide range of peripheral organ-specific antigens (Ags) in the medullary thymic epithelial cells (mTECs), which serve as self-Ags in negative selection. We examined the expression of desmoglein 3 (Dsg3), the autoantigen in pemphigus vulgaris (PV), in mouse thymus and the involvement of Aire in tolerance to Dsg3. Immunofluorescence and in situ hybridization revealed Dsg3 in single cells or in clusters in 3% of mTECs near the cortico-medullary junction of the thymus in C57BL/6 mice. Dsg3-expressing mTECs also expressed some Ags of skin-unrelated peripheral organs simultaneously. In contrast, Dsg3-positive mTECs were not detected in the Aire ^+/+ thymus. Adoptive transfer of splenocytes from Aire ^-/- mice immunized with Dsg3 did not induce anti-Dsg3 IgG production or PV phenotype in Rag2 / recipient mice. However, Aire / CD4 ⁺ T cells, but not Aire ^+/+ CD4⁺ T cells, induced low levels of anti-Dsg3 IgG production when transferred with Dsg3 / B cells. These findings indicate that Aire has an important role in Dsg3 expression as well as in selection of T cells that help B cells to produce anti-Dsg3 IgG in thymus.