Interestingly, many of these immune molecules either express specifically in microglia (e.g., the MS4As, CD33, SPI1, and INPP5D) or are enriched in microglial cells (e.g., CR1, ABCA7, and CLU), suggesting that microglia plays crucial role in the immune regulation of AD.247 Some of the molecules have been reviewed recently.248 However, for most of the molecules identified by GWAS, further studies are needed to verify the role of these molecules in the development and progression of AD. This evidence concerns the gene CD33 and Alzheimer disease.