HLA-DRB1 and Alzheimer disease: The genes driving the enrichment (gene-based P-values ≤ 0.01) of the microglial module are known AD-associated risk genes (CD33, GAL3ST4, HLA-DRB1, INPP5D, MS4A4A, SPI1 and TREM2) and putative risk genes (ITGAM, LAPTM5 and LILRB4)20,41 (Fig. 2 and Supplementary Table 1).