Mechanism of transport of rat immunoglobulin G (rIgG) across primary cultured rat alveolar epithelial cell monolayers

The goal of this study was to elucidate the mechanism of IgG transport across the rat alveolar epithelial cell monolayers. IgG transport was saturable and rapid, yielding net absorption of rIgG. The saturation data and the inhibition of transport in presence of excess Fc fragment indicate a receptor-mediated process identifying the Fc portion of IgG. Excess chicken IgY was unable to inhibit IgG transport, further supporting the possibility of FcRn involvement in IgG transport. The detection of the FcRn mRNA transcript also supports the hypothesis of FcRn mediated-transport. Regulation of IgG transport was investigated using 1 muM dexamethasone-treatment. Dexamethasone significantly inhibited IgG transport in the apical-to-basolateral direction by 50 and 62% after 48 and 72 hr of treatment, respectively.