Cytospin preparations showing EBER-1 in situ hybridization of the lymphocyte subpopulations. Lymphocyte subpopulations from patients 1 and 3 were separated by magnetic bead sorting after immunostaining with anti-CD4, CD8, CD19 or CD56 mAbs. EBV infection in each subpopulation was determined using EBER-1 ISH. A, In patient 1, EBER-1-positive cells (shown by their dark nuclear staining) were detected in34.0% of the B cells but were not detected in CD4+ T cells, CD8+ T cells or CD56+ NK cells (< 0.1% each). B, In patient 3, EBER-1-positive cells were observed in 75.5% of CD8+ T cells, 2.8% of CD19+ B cells, and 17.4% of CD56+ NK cells, but not observed in CD4+ T cells .