CD28 and Alzheimer disease: Despite the decrease in total CD3+CD4+ cell subpopulation in AD patients, these lymphocytes showed a marked elevation of CD152+ expression alone (6.6 ± 4.1 %) as well as co-expression of both CD152+ and CD28+markers (24.8 ± 11.7 %) as compared to controls (3.2 ± 2.6 %, p < 0.05 and 12.9 ± 7.9 %, p < 0.001, respectively).