IL-1α is the protein secreted by NTHi-treated HMEEC cells that is responsible for the transcriptional activation of the β-defensin 2 (DEFB4) promoter. Treated medium – 1:4 dilution of the conditioned medium from cells treated with NTHi lysate for 48 hours. Control medium (Con-M) – 1:4 dilution of conditioned medium from non-treated cells. Anti-IL-1α antibody (20, 40 and 80 μg/ml), but not pre-immune IgG, can block the transcriptional activation of the β-defensin 2 promoter in a dose dependent manner. Values are given as the mean ± standard deviation. N = 3. *: p < 0.05, **: p < 0.01.