CR2 and Alzheimer disease: In contrast, other researchers reported decreased values of CD5+, CD4+, CD8+, and CD21+ cells in groups of seropositive dogs (AD-II and SD) when compared to seronegative dogs (control healthy dogs (CD) and AD-I), despite the occurrence of clinical signs of CVL, with higher CD4+/CD8+ ratios in AD-I and SD [6].