COEXPRESSION OF FC-GAMMA RECEPTOR IIIA AND INTERLEUKIN-2 RECEPTOR-BETA CHAIN BY A SUBSET OF HUMAN CD3+ CD8+/CD11B+ LYMPHOCYTES/

In this study we identify and characterize a subset of human periphera l blood T cells, present in all individuals, that has features previou sly described for T cells either separately or in special circumstance s. These cells are found in purified suspensions of resting peripheral blood lymphocytes within the CD8+ T lymphocytes, express alphabeta T cell receptor (TCR), and can be identified and isolated because of hig h-density expression of surface CD11b (TCRalphabeta+/CD3+/CD8+/CD11bcells). They coexpress constitutively the IL-2 receptor beta chain, Fc gammaRIIIA, and CD56. Although they do not mediate spontaneous cytotox icity, CD3+/CD8+/CD11b+ cells have cytotoxic potential, demonstrated i n redirected cytotoxicity assays with P815 target cells in the presenc e of anti-FcgammaRIII (CD16) or anti-CD3 monoclonal antibodies. Stimul ation of CD3+/CD8+/CD11b+ cells with rIL-2 induces proliferation, cyto toxicity against NK-sensitive and NK-resistant target cells, and expre ssion of surface activation antigens, including IL-2 receptor alpha ch ain (CD25). CD3+/CD8+/CD16+/CD56+ cell clones with cytotoxic functions including those mediated by engagement of surface CD16 were obtained by limiting-dilution cloning of purified CD3+/CD8+/CD11b+ cells in the presence of rIL-2 and autologous feeder cells. Our data support the h ypothesis that the CD3/CD8+/CD11b+/CD16+ cells represent a discrete pe ripheral blood lymphocyte subset that could be the physiological count erpart of that expanded in several pathological conditions and in larg e granular lymphocyte lymphocytosis.