Studies on the mechanism of natural killer cytotoxicity. II. coculture of human PBL with NK-sensitive or resistant cell lines stimulates release of natural killer cytotoxic factors (NKCF) selectively cytotoxic to NK-sensitive target cells.

Abstract

This investigation has employed the "innocent bystander" type of experimental design to determine whether soluble cytotoxic factor(s) are released during interactions between human peripheral blood lymphocytes (PBL) and NK-sensitive target cells. PBL cocultured with NK-sensitive Molt-4 or K562 target cells in the lower well of a miniaturized Marbrook culture released natural killer cytotoxic factors (NKCF), which diffused across a 0.2-mu Nucleopore membrane and lysed Molt-4 or K562 target cells cultured in the upper chamber. Coculture of PBL with the NK-resistant Raji or WI-L2 cell lines also induced release of NKCF. These factors were selectively cytotoxic to NK-sensitive targets and lysed Molt-4 and, to a lesser extent, K562 cells. However, Raji, WI-L2, and RPMI 1788 cells were all resistant to lysis. In addition, low density fractions from Percoll density gradients that were enriched for NK effector cells also released increased levels of NKCF during coculture with Molt-4 cells. Lysis of Molt-4 and K562 targets was observed after exposure to NKCF for 48 hr and 60 to 70 hr, respectively. Cellfree supernatants containing NKCF were obtained after a short time of incubation (i.e., within 5 hr of coculture of PBL with NK target cells). The factors were nondialyzable, stable at 56 degrees C for 3 hr, and showed partial loss of activity on storage at 4 degrees C or -20 degrees C for 7 days. These data suggest that NKCF may be involved in the lytic mechanism of human NK cell-mediated cytotoxicity.

The human LT system. XI. Identification of LT and "TNF-like" forms from stimulated natural killers, specific and nonspecific cytotoxic human T cells in vitro.

“…7), The small peptide has been sequenced and cloned, and appears to be a component in both a-LT forms (8). Human natural killer (NK) cells stimulated with lectins or contact with target cells release LT forms, termed NK-LT or NK-CF (9,10). These forms are functionally different from other LT forms because they appear to be species-specific, bind and lyse NK-sensitive target cells, but do not lyse NK-resistant cells in vitro (9,10).…”

“…Human natural killer (NK) cells stimulated with lectins or contact with target cells release LT forms, termed NK-LT or NK-CF (9,10). These forms are functionally different from other LT forms because they appear to be species-specific, bind and lyse NK-sensitive target cells, but do not lyse NK-resistant cells in vitro (9,10). Our previous studies had shown that human T cells could release LT forms that appeared to be distinct from both a-LT and NK-CF forms (4).…”

The human LT system. XII. Purification and functional studies of LT and "TNF-like" LT forms from a continuous human T cell line.

“…This led to the concept that different populations of effector cells may be capable of releasing LT forms with different functional capabilities ( 1,11 ). This premise was supported by the discovery of cell lytic forms, termed NK-CF and NK-LT. that are immunologically distinct from a-LT, derived from natural killer (NK) effector cells, and more effective on NK-sensitive than on NK-resistant target cells in vitro (12,13).…”