At multivariate linear regression, plasma IL-4 levels were positively associated with left subiculum volume (β = 0.226, p = 0.037) in sMCI; contrarily, IL-4 levels were negatively associated with left subiculum volume (β = -0.253, p = 0.011) and left presubiculum volume (β = -0.257, p = 0.011) in AD. This evidence concerns the gene IL4 and Alzheimer disease.