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

肠上皮细胞（IECs）除了具有粘膜屏障和转运营养物质的功能外，还具有抗原提呈细胞（apc）的功能。通过蛋白水解修饰蛋白抗原是抗原呈递到Th细胞的主要步骤之一。我们使用Caco-2肠上皮细胞系研究了膳食抗原卵清蛋白（OVA）的经上皮转运。我们还研究了促炎细胞因子干扰素-γ (IFN-γ)在Caco-2细胞层中对抗原转运过程的影响。Caco-2细胞层将完整的和降解的OVA从粘膜转移到浆膜侧。IFN-γ刺激了卵细胞的转运，大部分转运的卵细胞被降解。我们还使用免疫组织化学方法检测了Caco-2细胞对OVA的摄取。Caco-2细胞以时间依赖的方式并入OVA， IFN-γ显著增强抗原内化。流式细胞术也显示IFN-γ增加了FITC-OVA的内化。我们还测定了低浓度和高浓度IFN-γ对粘膜通透性和FITC-OVA内化的影响。虽然10和50 ng/mL IFN-γ对粘膜通透性的刺激程度相同，但与10 ng/mL IFN-γ相比，50 ng/mL IFN-γ培养的Caco-2细胞内化了更多的FITC-OVA。这些结果表明，IFN-γ对肠上皮细胞粘膜通透性和抗原内化的影响可能通过不同的机制实现。因此，较高浓度的IFN-γ刺激iec对膳食抗原的摄取、加工和运输。

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.