The interaction of normal lymphocytes and cells from lymphoid cell lines. VI. Line-directed cytotoxic specificity of lymphocytes activated by autochthonous or allogeneic LCL cells.

Human peripheral blood lymphocytes activated by contact with X-irradiated cells from lymphoblastoid cell lines (LCL cells) acquire cytotoxic capacity directed against LCL cells as demonstrated by release of Cr from the labelled target. In a large series of cross-over experiments it was possible to demonstrate an element of specificity in the cytotoxic phase in the sense that lymphocytes activated by irradiated cells from line A' tended to kill target cells of line A' more efficiently than those of an unrelated line. This `line-directed' specificity was not absolute and in some experiments could not be demonstrated at all. Several factors could be identified which tend to obscure line-directed specificity. Both specific and non-specific cytotoxicity as observed in this system are probably relevant to the immunological defence of the intact organism against proliferating aberrant lymphoid cells.