Synergistic effect of hyperoxia and immunoglobulin A on mucosal barrier defense

Hyperoxia has been reported to be protective against gut-derived sepsis. Although secretory immunoglobulin A (IgA) is primarily responsible for humoral defense of mucosal surfaces, a potential synergistic effect with hyperoxia is unknown. An asanguineous cell monolayer system was used to study these aspects in vitro.

MDCK cells were grown as polarized monolayers in a two-chamber culture system. Apical chambers were inoculated with 10(8) Escherichia coli M14 with or without polyclonal IgA and incubated in a 21 or 95% O2 environment. Basal medium was sampled at 90 and 180 minutes for bacterial translocation. In a second experiment, MDCK cells were lysed at 90 minutes and intracellular bacteria were quantitated.

Bacterial translocation was decreased versus normoxia by the treatment groups IgA without hyperoxia or IgA with hyperoxia at 90 minutes. Bacterial internalization at 90 minutes was reduced to the greatest extent by the combined effects of hyperoxia and IgA. Translocation data at 180 minutes confirmed the additional protective effect of hyperoxia with IgA.

Hyperoxia exerts a significant protective effect on barrier function independent of enhanced leukocyte function. Hyperoxia has an added effect to the mucosal defense provided by IgA.