Clonally restricted natural killer-like cytotoxicity displayed by cloned human T cell lines.

Abstract

Cloned human T cell lines were produced by lymphocytes alloactivated in mixed leukocyte cultures by using the technique of limiting dilution followed by expansion of clonal progeny with interleukin 2. This methodology allowed cloning efficiencies of >50% when cells were seeded at 0.3 to 0.45/well. The cloned cells were tested for cell-mediated cytotoxicity (CTX) in 51Cr-release assays against a variety of human cell lines targets (MOLT4, K562, 1301, HSB2 and JM) known to be susceptible to lysis by natural killer (NK) cells. Fifteen out of 105 clones tested were found to lyse cell lines targets, but they lacked or had insignificant CTX against normal peripheral blood leukocytes, PHA-pretreated normal lymphocytes, B cell lines, or T cell lines from donors of either the MLC-stimulating or the MLC-responding (autologous) cells. Moreover, unlabled cultured T cells or B cells of stimulator origin were unable to inhibit specific 51Cr release from K562 target cells, demonstrating that the determinants recognized by clones lysing K562 cells were not expressed on normal cells. In contrast, cloned cells with allospecific CTX were inhibited by normal lymphocytes but not by K562 cells. The patterns of CTX of clones lysing NK-susceptible targets were thus different from those manifested by so-called anomalous killers, and because they most closely resembled natural killing by fresh lymphocytes, were designated NK-like. With a single exception, all the NK-like clones lysed K562 targets but had different patterns of cytotoxicity on the other susceptible targets. One clone, however, failed to lyse K562, MOLT4, 1301, or MJ and was cytotoxic only to HSB2 cells. Furthermore, neither unlabeled K562 nor cultured stimulator T cells competed with HSB2 targets for this clone. These results strongly suggest a clonal distribution of receptors for different NK-like target determinants in human NK-active T cell clones.