Immune response towards the amino-terminus of desmoglein 1 prevails across different activity stages in nonendemic pemphigus foliaceus

Summary Background Pemphigus foliaceus (PF) is a blistering skin disease mediated by antibodies to desmoglein (Dsg) 1. The two major subtypes are nonendemic and endemic PF. A previous study in endemic PF demonstrated that changes in antibody epitope could modulate disease relapse and remission. Objectives To characterize the frequency of immunoreactivity to various Dsg1 extracellular (EC) domains in nonendemic PF and to study if there is any change in epitope profile across various activity stages. Methods Sera from 34 patients with nonendemic PF were selected. To map the conformational epitopes by immunoprecipitation‐immunoblotting, we constructed five Dsg1/Dsg2 domain‐swapped molecules, with each molecule representing one EC domain of Dsg1 on a backbone of Dsg2. Results Dsg1 EC1, EC2, EC3, EC4 and EC5 domains were recognized by 88%, 50%, 13%, 22% and 0% of active PF sera, respectively. Immunoreactivity to EC3 or EC4 often cosegregated with that to either EC1 or EC2. Longitudinal follow‐up of 21 patients with PF for a median of 16 months revealed that, in most cases, immunoreactivity to the amino‐terminus of Dsg1 persisted across various activity stages; only two patients lost their EC1 reactivity upon remission and changed their major epitope(s) to EC2 ± EC3. Conclusions Most of the anti‐Dsg1 antibodies in nonendemic PF bind to the amino‐terminus of Dsg1, a region critical for intercellular adhesion of cadherins, and this skewed amino‐terminal immunoreactivity prevails across various activity stages in most patients, even upon remission. These findings are valuable for understanding the biology of Dsg‐mediated cellular adhesion as well as for the development of epitope‐based monitoring and therapeutic strategies.