The testing of four different CCD-expressing proteins by ELISA using the serum of 34 dogs with AD first revealed that 14 of them (41.2%) had detectable anti-CCD IgE in their serum, a percentage that is in the middle of the range (17% [12] to 73% [11]) previously reported in other studies that tested sera from allergic dogs. Here, IGHE is linked to Alzheimer disease.