Effect of OsM on AAT polymers formation in ex-vivo cultured BECs. ELISA for polymeric AAT protein, using the ATZ11 antibody, in cell culture media and cell lysates of ex vivo cultured BECs from Z-AAT homozygous patients. Cells from five patients were incubated in the absence (OsM-) and presence (OsM+) of Oncostatin M (50 ng/ml) for 24 hours, and AAT secretion and intracellular accumulation were measured in the 10x concentrated cell medium. Results are expressed as mean absorbance ± SEM (n = 3–4), measured at 450 nm. *P = < 0.01 Student’s t-test. Definition of abbreviations: AAT = alpha-1 antitrypsin; BEC = bronchial epithelial cell; ELISA = enzyme-linked immunosorbent assay; SEM = standard error of mean.