Pemphigus vulgaris (PV) is an autoimmune blistering disease of the skin and is caused by autoantibodies against desmoglein 3 (Dsg3) on epidermal keratinocytes. Because the production of autoantibodies is presumably T cell dependent, Dsg3-specific T cell reactivity was investigated in 14 PV patients and 12 healthy donors. Peripheral blood mononuclear cells from seven PV patients with active disease showed a primary in vitro response to a recombinant protein containing the extracellular portion (EC1-5) of Dsg3, whereas two of seven PV patients in remission or under immunosuppressive treatment exhibited only secondary (2°) or tertiary (3°) T cell responses to Dsg3. T cell responses to Dsg3 were also observed in four of 12 healthy individuals upon 2°or 3°stimulation with Dsg3. Both PV patients and healthy responders were either positive for DRβ1*0402 - which is highly prevalent in PV - or positive for DR11 alleles homologous to DRβ1*0402. Two CD4 + Dsg3-specific T cell lines and 12 T cell clones from two PV patients and two CD4 + T cell lines and eight T cell clones from two normals were also stimulated by a Dsg3 protein devoid of the EC2-3 (ΔN1), suggesting that epitopes were located in the EC1, EC4, and/or EC5. Using Dsg3 peptides, one immunodominant peptide (residues 161-177) was also identified in the EC2. These observations demonstrate that T cell responses to Dsg3 can be detected in PV patients and in healthy donors carrying major histocompatibility class II alleles identical or similar to those highly prevalent in PV.
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