IGHG3 and Cognitive impairment: We examined HSV-1-specific IgG3 titers in serum of AD (n = 70) and mild cognitive impairment (MCI) (n = 61) subjects comparing the results to those of 67 age- and sex-matched healthy controls (HC); associations between MRI-determined brain cortical health and HSV-1-specific IgG3 were analyzed in a subgroup of AD and MCI subjects.