Natural killer cells express an Fc receptor for IgG (CD16) in association with disulflde-linked dimers composed of two homologous subunits: the ζ chain of the T cell antigen receptor complex and the γ chain of the mast cell/basophil Fc receptor for IgE. The ability of ζ and γ to transduce CD16-mediated activation signals was compared by reconstituting distinct CD16 receptor Isoforms composed of various combinations of ζ- and γ-containlng dimers. Stably transformed non-hematopoietic and hematopoletic cell lines were established that expressed chlmerlc molecules comprising the extracellular domain of CD16 Joined to the transmembrane and Intracellular domains of ζ or γ. Reconstituted CD16 receptor complexes triggered Ca2+ influx, tyroslne phosphorylatlon, and IL-2 production In stable transformants of the Jurkat T cell line. However, cross-linking of the CDI6/γ chimera induced a specific pattern of tyrosine phosphorylatlon and was more efficient at signal transductlon than a CD16, ζ-ζ complex, suggesting that ζ and γ cytoplasmlc domains may be coupled to distinct tyroslne klnase pathways that differentially regulate CD16-medlated activation signals. By contrast, both CD16/ζ and CDI6/γ chimeric molecules were not functional in stable transformants of the flbroblast Chinese Hamster Ovary cell line, Indicating a requirement for downstream signaling components present In hematopoletic cells. Finally, the ζ transmembrane domain appears to preferentially associate with CD16 rather than the CD3: TCR complex, suggesting that a hierarchy of molecular interactions governs NK and T cell differentiation.