Synergistic effect of hyperoxia and immunoglobulin A on mucosal barrier defense

Background: Hyperoxia has been reported to be protective against gut-derive d sepsis, Although secretory immunoglobulin A (IgA) is primarily responsibl e for humoral defense of mucosal surfaces, a potential synergistic effect,w ith hyperoxia is unknown. An asanguineous cell monolayer system was used to study these aspects in vitro. Methods: MDCK cells were grown as polarized monolayers in a two-chamber cul ture system. Apical chambers were inoculated with 10(8) Escherichia coli M1 4 with or,without polyclonal IgA and incubated in a 21 or 95% O-2 environme nt. Basal medium,vas sampled at 90 and 180 minutes for bacterial translocat ion, In a second experiment, MDCK cells were lysed at 90 minutes and intrac ellular bacteria were quantitated, Results: Bacterial translocation was decreased versus normoxia by the treat ment groups IgA without hyperoxia or IgA with hyperoxia at 90 minutes. Bact erial internalization at 90 minutes was reduced to the greatest extent by t he combined effects of hyperoxia and IgA, Translocation data at 180 minutes confirmed the additional protective effect of hyperoxia with IgA, Conclusion: Hyperoxia exerts a significant protective effect on barrier fun ction independent of enhanced leukocyte function. Hyperoxia has an added ef fect to the mucosal defense provided by IgA.