EBV is detected in plasmablasts/plasma cells and T cells. (A) Photomicrographs of PBMCs stained by Immuno-FISH from patient 4 shows EBV in plasmablasts/plasma cells identified using Alexa 647–conjugated anti-κ and anti-λ chain immunoglobulin antibodies. The EBV-positive cells are negative for CD20 using Alexa 488–conjugated anti-CD20 antibody. EBV DNA was identified with the biotinylated FISH probe and streptavidin-conjugated Alexa 594 and monocytes with V450-conjugated anti-CD14 antibody. Although most of the EBV DNA was detected in the nucleus, some viral DNA was detected in the cytoplasm, suggesting that EBV lytic infection was present in the cell. (B) Photomicrographs of PBMCs stained by Immuno-FISH from patient 12 shows EBV in CD3⁺ T cells. EBV DNA was identified with biotinylated FISH probe and streptavidin-conjugated Alexa 488, B cells using a combination of Alexa 647–conjugated anti-CD19 and anti-CD20 antibodies, T cells with Alexa 594–conjugated anti-CD3 antibody, and monocytes with V450-conjugated anti-CD14 antibody. Arrows indicate EBV-positive cells.