INDUCTION OF MHC CLASS-II ANTIGENS ON RAT BRONCHIAL EPITHELIAL-CELLS BY INTERFERON-GAMMA AND ITS EFFECT ON ANTIGEN PRESENTATION

Recent studies have found aberrant expression of class II antigens by. bronchial epithelial cells (BECs), suggesting that these cells may al so be involved in airway mucosal immunity. However, the regulation of class II antigen expression on BECs by cytokines and the functional ca pacity of such cells bearing class II molecules remain unknown. We inv estigated the effect of IFN-gamma on class II antigen expression by cu ltured rat BECs, as well as the ability of these cells to present inta ct protein antigens to specifically sensitized T cells. Although prima ry BECs did not express class II antigens, IFN-gamma readily induced t heir expression in a dose-dependent manner. More than 85% of the BECs treated with 1000 U/ml of IFN-gamma were positive for class II antigen s. In addition, when IFN-treated BECs bearing class II molecules were pulsed with ovalbumin (OVA), they significantly stimulated the prolife ration of OVA-sensitized T cells, whereas cells that were not treated with IFN-gamma but were pulsed with OVA did not do so. Our findings in dicate that BECs bearing class II molecules are capable of presenting OVA to OVA-sensitized T cells. These results suggest that various path ological conditions causing the local production of IFN-gamma may incr ease class II antigen expression on BECs, which in turn may modulate t he airway mucosal immune response by the presentation of antigens to T cells.