This intrinsic property of IgG4 antibodies can either enhance the pathogenicity of autoantibodies, as observed with MuSK autoantibodies (112, 121–123), without significantly affecting their effects as seen in CNTN1 autoantibodies and pemphigus (142, 151, 161) or diminish their pathogenic potential as seen with anti-Neurofascin-155 IgG4 (141). This evidence concerns the gene MUSK and pemphigus.