ANALYSIS OF CD16+DIM AND CD16+BRIGHT LYMPHOCYTES - COMPARISON OF PERIPHERAL AND CLONAL NON-MHC-RESTRICTED T-CELLS AND NK-CELLS

The Fc-gamma-RIII receptor (CD16) had been described on natural killer cells and a small subset of T lymphoctyes. CD16+bright lymphocytes represent the typical population of peripheral blood CD3- NK cells. In these studies in addition to CD16+bright NK cells Fc-gamma-RIII expressing cytotoxic T lymphocytes in peripheral blood from one healthy individual are characterized as CD16+dim non-MHC-restricted CTLs either expressing the alpha-beta (80%) or the gamma-delta T cell receptor (20 %). Both CD16+ subsets are clearly distinct on their functional capacity performing NK and ADCC activity. Freshly isolated CD16+dim T cells exert higher ADCC, CD16+bright NK cells higher Nk activity. They are also differentially activated by interleukin-2 since CD16+bright NK cells reveal a bright expression of the p75 IL-2 receptor beta-chain in contrast to the very low p75 expression on CD16+dim T cells. This activation leads to a gradual increase of the ADCC by NK cells. Finally the CD16 expression pattern with low and bright intensity represents a stable phenotype expressed by clones generated from these different subpopulations. On a clonal level CD16+dim non-MHC-restricted T cells can be distinguished from CD16+bright NK cells by their lower capacity in NK killing, but they equally potent in ADCC. Finally these CD3+ CD16+dim clones provide the basis for studies of Fc-gamma-RIII and TcR interaction.