Of potential relevance to the age 1-year peak incidence of islet autoimmunity, there was a two-fold enrichment of T1D susceptibility genes, including MHC genes, among those with age-related expression changes and this enrichment was pronounced for genes that had trajectories mirroring the islet autoantibody incidence (Cluster B). This evidence concerns the gene HLA-C and type 1 diabetes mellitus.