Background: Human leukocyte antigen (HLA)-G is a nonclassical class I antigen with immunomodulatory roles\r\nincluding up-regulation of suppressor T regulatory lymphocytes. HLA-G was recently identified as an asthma\r\nsusceptibility gene, and expression of a soluble isoform, HLA-G5, has been demonstrated in human airway\r\nepithelium. Increased presence of HLA-G5 has been demonstrated in bronchoalveolar lavage fluid recovered from\r\npatients with mild asthma; this suggests a role for this isoform in modulating airway inflammation though the\r\nmechanisms by which this occurs is unclear. Airway inflammation associated with Th2 cytokines such as IL-4 and\r\nIL-13 is a principal feature of asthma, but whether these cytokines elicit expression of HLA-G is not known.\r\nMethods: We examined gene and protein expression of both soluble (G5) and membrane-bound (G1) HLA-G\r\nisoforms in primary differentiated human airway epithelial cells collected from normal lungs and grown in air-liquid\r\ninterface culture. Cells were treated with up to 10 ng/ml of either IL-4, IL-5, or IL-13, or 100 ng/ml of the\r\nimmunomodulatory cytokine IL-10, or 10,000 U/ml of the Th1-associated cytokine interferon-beta, for 24 hr, after\r\nwhich RNA was isolated for evaluation by quantitative PCR and protein was collected for Western blot analysis.\r\nResults: HLA-G5 but not G1 was present in dAEC as demonstrated by quantitative PCR, western blot and confocal\r\nmicroscopy. Neither G5 nor G1 expression was increased by the Th2-associated cytokines IL-4, IL-5 or IL-13 over\r\n24 hr, nor after treatment with IL-10, but was increased 4.5 �± 1.4 fold after treatment with 10,000 U/ml interferonbeta.\r\nConclusions: These data demonstrate the constitutive expression of a T lymphocyte regulatory molecule in\r\ndifferentiated human airway epithelial cells that is not modulated by Th2-associated cytokines.
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