DSG1 and pemphigus foliaceus: To investigate the impact of IgG4 subclass on the pathogenicity of anti-Dsg1 autoantibodies, we studied anti-Dsg1 autoantibodies previously isolated from PF patients and proven to be pathogenic in both neonatal mouse and human tissue-culture models (Ishii et al., 2008; Yamagami et al., 2009).