Activation of STAT1 and STAT3 in IgA1-secreting tonsillar cell lines by LIF or OSM. (a) Representative blots show phosphorylation of STAT1 (pSTAT1) (Y701) after 5-, 15-, 30-, and 60-minute stimulation with LIF (left panels) or OSM (right panels). Total STAT1 protein served as a loading control. Baseline pSTAT1 was enhanced in cells from IgAN group compared to those from OSA group. Treatment with LIF further enhanced pSTAT1 at different time points, reaching peak at 15 minutes. Treatment with OSM did not induce significant changes of pSTAT1 at different time points. STAT3 was not phosphorylated in any of the tested groups at baseline or after LIF or OSM stimulation. (b) Densitometric analyses of pSTAT1 normalized to total STAT1 (n = 3 in each group). pSTAT1 relative to total STAT1 level in OSA samples (control) was set to 1 for the comparisons. Actin blot is shown as an additional control for protein load. All data are presented as mean ± SD values and mean values for individual cell lines are shown by black circles. ∗P < 0.05. IgAN, IgA nephropathy; ns, not statistically significant; LIF, leukemia inhibitory factor; OSA, obstructive sleep apnea; OSM, oncostatin M.