Given the increased abundance of IgG4 immunoglobulins among CD83(+) AD subjects, including evidence suggestive of anti‐HCMV specificity and HCMV in the TC, we hypothesized that either IgG4 or HCMV itself may be directly inducing CD83(+) microglia in the SFG. This evidence concerns the gene CD83 and Alzheimer disease.