Abstract
We found a phenomenon that T-cells bearing receptors for the Fc portion of IgG (TG-cells) show cytotoxicity against cultured lymphoid cell lines bearing Fc (IgG) receptors and designated as immune complex dependent T-cell mediated cytotoxicity (IDTC). TG-cells are also known to work as effectors ofs pontaneous cytotoxicity (SC). However, these two phenomena seemed to be distinct from each other, since IDTC worked even at low effector/target (E/T) ratio while higher E/T ratio was required for SC and IDTC activity was lost by the treatment of TG-cells with mitomycin C (MMC) while SC activity was resistant to MMC. Various cell lines were studied for their sensitivity to SC by ^51Cr relerase, inhibition of DNA synthesis and inhibition of cell growth. Some were lysed but some other were only inhibited of DNA synthesis or cell grouwth and theremining showed resistance. These observation indicase that there is the difference of sensitivity to SC among cell lines. Cord TG-cells usually showed IDTC but only few cases had cytolytic activity by SC. Some showed SC only when they were assayed by inhibition of DNA synthesis or cell growth.
