An elegant study by Quesada-Masachs in 2021 showed that HLA class II proteins were found in 24.31% of insulin-containing islets of T1D donors, almost half of HLA class II signal was colocalized with insulin and 27.5% of these islet cells coreleased HLA class II molecules with insulin (Quesada-Masachs et al, 2022). The gene discussed is INS; the disease is type 1 diabetes mellitus.