IFNG and asthma: The hypothesis regarding altitude is that it significantly reduces the level of exhaled nitric oxide (NO), a determinant of inflammation of the local airways in patients with moderate or severe intrinsic asthma; increases blood levels of interleukin 10 (a cytokine with powerful anti-inflammatory properties) and decreases the concentration of interferon-γ (IFN-γ), responsible for inflammation of the local airways.