Early interest in autoantibodies in T1D, before the advent of scRNAseq, focussed on isolating GAD-specific B cells from people with T1D (62) and sequencing the BCRs from clones, which provided evidence that GAD autoantibodies have frequently undergone somatic maturation and are therefore from antigen-experienced B cells (63, 64). Here, GAD1 is linked to type 1 diabetes mellitus.