Increased percentage of circulating CD3ζ− CD8 T cells in otherwise healthy subjects during acute viral infection.

(A) Three healthy donors were analyzed for CD8 T cell CD3ζ chain expression before, during, and after recovery from 3 different acute viral infections. Subject AI-1 had acute EBV infection, AI-2 had EBV–CMV– infectious mononucleosis syndrome, and AI-3 had presumed viral gastroenteritis. The percentage of CD3ζ− CD8 T cells in freshly isolated PBMC was determined by flow cytometry on gated lymphocytes using CD20+ B cells as an internal CD3ζ− population to set the CD3ζ gate. Day 1 corresponds to the onset of symptoms; day 1 samples were obtained from subjects 1 and 3 before they knew they were becoming ill. At time points before day 1, the subjects had been studied as normal controls. (B) Representative flow cytometry dot plots on gated lymphocytes, dually stained with PE-conjugated antibodies to CD20, CD3ε, CD4 or CD8, and CD3ζ− FITC, are shown for 2 normal donors. (C) Similar analysis for subject AI-1 on samples obtained either several months before the onset of symptoms or on days 1, 6, 19, and 67 after the onset of symptoms. Three-color staining with antibodies to CD3ε, CD3ζ, and CD8 in some samples (not shown) corroborated that the CD8+CD3ζ− cells are CD3ε+ T cells.