10-month-old APOE3-TR mice had highest IgG levels in various brain regions, while the IgG levels were significantly lower in brain regions severely affected by AD (neocortex, entorhinal cortex and hippocampus), but not in relatively intact brain regions (thalamus and cerebellum) of 10-month-old female APOE4-TR mice. This evidence concerns the gene APOE and Alzheimer disease.