SUBSETS OF CD8-INDIVIDUALS - CORRELATIONS WITH HUMAN CYTOMEGALOVIRUS (HCMV) CARRIER STATUS, PHENOTYPIC AND FUNCTIONAL ANALYSES(, CD57+ CELLS IN NORMAL, HEALTHY)

Two different subsets of CD8+, CD57+ cells have been defined, one expr essing high levels (CD8high+(CD57+)), the other expressing low levels of surface CD8 (CD8low+(CD57+)). Increased numbers of CD8high+(CD57+) cells correlated with previous HCMV infection. By three-colour fluores cence analysis, the CD8high+(CD57+) population expressed T cell marker s such as CD3 and CD5, and most were alphabeta T cell receptor (alphab eta TCR)-positive. A significant proportion also expressed CD71 (trans ferrin receptor) and MHC class II, although little if any CD25 (IL-2R- p55). Some (greater-than-or-equal-to 40%) co-expressed CD45RA and CD45 RO. The CD8low+(CD57+) population expressed classical natural killer ( NK) cell markers-CD2, CD16 and CD56. The two subsets were also functio nally distinct; CD8high+(CD57+) cells suppressed pokeweed mitogen (PWM )-driven, but not phytohaemagglutinin (PHA)-driven proliferation and i mmunoglobulin production; CD8low+(CD57+) cells exhibited NK cytotoxic activity which was not increased by interferon-alpha (IFN-alpha). Supe rnatant from cultured CD8high+(CD57+) cells suppressed PWM-driven immu noglobulin production, but not proliferation, and this effect was abro gated by physical separation with tissue culture inserts. Thus, a T ce ll subset expressing activation and memory T cell markers with direct non-specific suppressor activity was present in peripheral blood monon uclear cells (PBMC) of healthy subjects with asymptomatic HCMV infecti on.