A gamma-chain complex forms a functional receptor on cloned human lymphocytes with natural killer-like activity

We have recently derived from human fetal blood (25 wks) a series of cloned cell lines that were selected for their ability to kill the conventional natural killer (NK) target cell K562. It was found that a fraction of these clones express CD3 proteins but not the monomorphic Ti alpha beta determinant recognized by WT31 antibody. One interleukin-2-dependent CD3+ WT31- clone, termed F6C7, was used for immunization of mice to generate monoclonal antibodies directed at a potentially novel recognition receptor. It was shown that F6C7 cells, which transcribe Ti beta but not Ti alpha genes, surface-express a clonotypic structure, termed NKFi. Immunoprecipitations performed with anti-NKFi monoclonal antibody (mAb) indicated that the corresponding molecule is resolved in SDS-polyacrylamide gel electrophoresis (PAGE) as a single band of relative molecular mass approximately 85,000 (Mr approximately 85K). After reduction, a major band was detected at 44K and a faint band was present at 41K. The present study was designed to characterize this structure. It was found that NKFi represents either two 44K disulphide-linked gamma (TCR) chains, or possibly one gamma chain associated to an additional undetected molecule, and that the 41K material corresponds to a partially glycosylated fraction of the gamma protein. Anti-NKFi mAb both induces a specific autocrine proliferative response and blocks cytotoxic function, demonstrating that gamma chains serve as functional receptor structures on subpopulations of normal human lymphocytes.