Treatment of well-differentiated hTBE cells with Ps. a. culture filtrates induced IL-8 secretion and was non-toxic. A) The apical surface of well-differentiated hTBE cell culures was challenged with the indicated concentration of Ps. a. filtrate or 20% TSB as a control (0% Ps. a. group) in the presence of 10% human serum, and IL-8 was measured in the 24-hour conditioned basolateral medium. The results are the mean + SEM from 3 independent experiments with cell cultures from 3 different donors. B and C) Ps. a. filtrate was essentially non-toxic as illustrated by lack of LDH secretion into the medium and retention of cellular LDH. The results are from three replicate wells (mean + SD).