Immunohistochemistry P24/CD8 and P24/CD68 double staining of HAD and HIV non-dementia patients. Immunohistochemistry P24(brown)/CD8(red) and P24(brown)/CD68(red) double staining of HAD (patient A: a and b, patient B: c and d) and HIV non-dementia (patient c: e and f, patient d: g and h) patients in medulla region. Extensive P24 staining was observed in HAD patients (a, b, c and d) but was entirely absent in HIV non-dementia patients (e, f, g and h). It was also noticed that CD68+ macrophages co-localized with P24 (b and d) within HAD patients, whereas the co-localization of CD8 and P24 is much less pronounced (a and c). Most infected cells were macrophages (b and d), although there were still few CD8+ T cells infected as well. We observed noticeable CD8 (e and g) and CD68 (f and h) positive cells in HIV non-dementia patients, especially around the perivascular area, but these cells were negative for P24 antigen in all the brain regions studied for all 4 HIV non-dementia patients.