Endothelin-1 influence of DC function. (A) ET_A receptor blockade decreases the ability of mature DCs to stimulate T-cell proliferation in mixed leukocyte reaction (MLR). DCs were matured with S aureus treatment (DC + SA) for 48 hours. Mature DCs were treated either with ET_A receptor antagonist (DC + SA + ABT-627) or with ET_B receptor antagonist (DC + SA + A-192621). Different DCs were used in MLR to stimulate T-cell proliferation at different DC/T-cell ratios, and T-cell proliferation was assessed on the beta-counter by radioactive thymidine (³H-TdR) uptake. Results of 1 representative experiment of 5 are presented as mean ± SEM. (B) IL-12 production by DCs. Stimulation of DCs with S aureus (DC + SA) resulted in increased production of IL-12, as expected. Blockade of ET_A receptor on mature DCs (DC + SA + ABT-627) led to statistically significant drop in IL-12 production. Blockade of ET_B receptors (DC + SA + A-192621) had no significant effect on IL-12 production. ^*Statistically significant difference (P < .05) in IL-12 production between mature DCs and mature DCs with the ET_A receptor blockade.