FOOD ALLERGEN TRANSPORT BY HUMAN INTESTINAL CELLS : A STUDY USING CULTURED CACO-2 CELLS

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Besides functioning as a mucosal barrier and transporting nutrients, intestinal epithelial cells (IECs) also serve as antigen presenting cells (APCs). Modification of protein antigens by proteolysis is one of the principal steps in antigen presentation to Th cells. We used a Caco-2 intestinal epithelial cell line to investigate the transepithelial transport of the dietary antigen, ovalbumin (OVA). We also examined in Caco-2 cell layers, the effects of the proinflammatory cytokine interferon-γ (IFN-γ) on the antigen transport process. Caco-2 cell layers transferred both intact and degraded OVA from the mucosal to the serosal side. IFN-γ stimulated OVA transport and most of the transported OVA in such cells was degraded. We also examined OVA uptake by Caco-2 cells using immunohistochemical means. Caco-2 cells incorporated OVA in a time-dependent manner and IFN-γ significantly enhanced antigen internalization. Flow cytometry also demonstrated that IFN-γ elevated the internalization of FITC-OVA. We also determined the effect of low and high concentrations of IFN-γ on mucosal permeability and internalization of FITC-OVA. Although both 10 and 50 ng/mL IFN-γ stimulated mucosal permeability to same extent, more FITC-OVA was internalized by Caco-2 cells incubated with 50, than with 10 ng/mL IFN-γ. These results suggest that the effects of IFN-γ on mucosal permeability and on the internalization of antigens by intestinal epithelial cells are brought about by different mechanisms. Therefore, higher concentrations of IFN-γ stimulates the uptake, processing and transport of dietary antigens by IECs.