GAD1 and type 1 diabetes mellitus: A further 2020 study assessed the presence in IVIG preparations of anti-neuronal IgG autoantibodies against glutamic acid decarboxylase (GAD) and aquaporin-4 (AQP4), in titers similar to those of patients with type 1 diabetes and NMOSD, respectively; however, these IVIG-related autoantibodies seem to target only linear epitopes, being part of the natural humoral immune repertoire and, thus, not playing a definite pathogenic role interacting with structural epitopes, as demonstrated by animal passive transfer models [260].