The human LT system. VII. Release of soluble forms and delivery to target L-929 cells by lectin-preactivated human lymphocytes in the absence of protein synthesis and secretory processes.

We have investigated the effects of inhibitors of cellular protein synthesis (emetine, cycloheximide) and secretion (colchicine, cytochalasin B) on the capacity of primary or secondary lectin-activated human lymphocytes to release LT molecules or to cause lectin-induced destruction (LICC) of murine L-929 cells in vitro. Our findings reveal: (a) agents which inhibit protein synthesis or secretion block the release of LT activity into the supernatant and LICC when primary lectin-stimulated human adenoid lymphocytes are employed as effector cells; (b) these same agents are ineffective at blocking LT release or LICC when 3- or 5-day lectin-prestimulated lymphocytes are employed; and (c) anti-human α-LT serum blocks LICC of L-929 cells mediated by primary or secondary lectin-activated human lymphocytes. The difference in participation of effector cellular processes in LICC between primary and secondary lectin-stimulated cells correlates with the findings that preactivated lymphoid cells possess high levels of preformed intracellular, as well as membrane associated, LT molecules, and that release of these materials into the supernatant or delivery to the target cell can occur independently of active protein biosynthesis or classical secretory systems.