Sequential TNF and TGF-beta regulation of expansion and induction of cytotoxicity in long-term cultures of lymphokine-activated killer cells.

Therapeutic use of lymphokine-activated killer (LAK) cells frequently requires higher numbers of effector cells than can be produced in short-term cultures. Extended stimulation of these cells by interleukin-2 (IL-2) past 2 weeks leads to a decrease in cytolytic activity and cell proliferation. To determine how known regulatory cytokines are involved in the mechanism responsible for loss lf IL-2 responsiveness, adherent LAK (A-LAK), nonadherent LAK (NA-LAK), monocyte-depleted (MD-LAK), and unmanipulated LAK (UN-LAK) cells derived from human peripheral blood were stimulated with high-dose IL-2 for 4 weeks, and cytokine production was measured serially. Despite continued supplementation with IL-2, cell number plaeaued at 2 weeks with a 2.5-3.0 log increase in A-LAK cultures and a 1.0 log increase in NA-LAK, MD-LAK, and UN-LAK cultures. Cytolytic activity had decreased significantly in all four culture systems after only 14 days of stimulation with IL-2 as assessed by the chromium release assay using K562, Daudi, and RP-mel tumor cell lines as targets, and LAK activity was barely detectable after 28 days of stimulation. Bioactive tumor necrosis factor (TNF) was present in concentrations of 15-55 U/ml during the first week of culture and at less than 10 U/ml thereafter. Bioactive transforming growth factor-beta (TGF-beta) was detected at 1-36 U/ml from 5 to 14 days of culture and decreased thereafter. Immunoreactive TGF-beta 2 was still present at concentrations of 20-90 pg/ml after 21 days of culture.(ABSTRACT TRUNCATED AT 250 WORDS)