In this context, the paired immunoglobulin-like type 2 receptor alpha (PILRA), an inhibitory immunoglobulin receptor involved in the regulation of the immune system and a co-receptor of herpes simplex virus type 1 (HSV-1), is related to dysfunctions in microglial activation and may represent a link to infectious factors that have been connected to AD [24,54,55]. Here, PILRA is linked to Alzheimer disease.