GAD1 and type 1 diabetes mellitus: The beta-cell's attack happens when T cells recognize autoantigens such as glutamic acid decarboxylase (GAD), islet cell autoantigen 69 (ICA69), insulinoma-associated antigen 2 (IA2), islet-specific glucose-6-phosphatase catalytic subunit–related protein (IGRP), and proinsulin, which are widely accepted as the initiating autoantigens in T1D (4, 5).