FC‐19 Autoantibodies against extracellular domains of desmocollin 1 are not involved in canine pemphigus foliaceus

Abstract

Pemphigus foliaceus (PF) is an autoimmune skin disease of dogs and humans. In human PF, the autoimmune target has been identified as desmoglein (Dsg) 1, a desmosomal cell–cell adhesion molecule, whereas the target in canine PF has not been identified. Many studies have suggested the possibility of Dsg1 being the target molecule. However, the pathological characteristics are similar to those of SPD type IgA pemphigus in humans, the target molecule of which is desmocollin (Dsc) 1. In this study, we attempted to clone canine Dsc1 and investigated whether canine PF sera could recognize Dsc1. Total RNA was purified from the muzzle skin of a healthy dog, and the cDNA of Dsc1 was amplified by RT‐PCR. Sequence analysis showed that the open reading frame of the extracellular domain of Dsc1 consisted of 695 amino acids and shared 82 and 79% amino acid identities with human and mouse Dsc1, respectively. The recombinant extracellular domain of Dsc1 was expressed by transient transfection with CHO cells. We used six canine PF sera: four sera that were positive in the indirect immunofluorescence test, two sera that were negative, and two normal canine sera. Immunoprecipitation‐immunoblotting analysis revealed that no canine PF sera or normal sera showed affinity for recombinant Dsc1. Although the tested sera were limited, the results suggest that no autoantibodies against the extracellular domain of Dsc1 were involved in the pathogenesis of canine PF and that another cell surface molecule may be involved. Funding: Self‐funded.