Background & aims: The immunoregulatory properties of primary colonic epithelial cells (CECs) have not been defined. The ability of CECs from wild-type and interleukin 2-deficient (IL-2(-/-)) mice to take up a complex protein antigen and present peptides via MHC molecules to T cells was assessed and contrasted with that of primary small intestinal epithelial cells (SIECs).
Methods: Uptake of fluorescein isothiocyanate (FITC)-labeled ovalbumin (FITC-OVA) by CECs and SIECs from wild-type and IL-2(-/-) mice was measured by flow cytometry. The effect of disrupting cytoskeleton organization and metabolic activity of CEC on antigen uptake was assessed. An OVA/I-A(b)-specific CD4(+) T-cell line transfected with an NFAT-lacZ reporter gene construct was used to evaluate the ability of CECs and SIECs as well as CECs from healthy and colitic IL-2(-/-) mice to present antigen to T cells.
Results: Uptake of FITC-OVA by CECs is concentration dependent, is not saturated at physiologic concentrations, and requires metabolically active cells. CECs from IL-2(-/-) mice take up significantly more antigen than those from wild-type mice. CECs are more efficient APCs than SIECs, and antigen-pulsed CECs from IL-2(-/-) mice induce the highest levels of T-cell activation.
Conclusions: Primary CECs are efficient APCs for CD4 MHC class II-restricted T cells. Antigen uptake and presentation is up-regulated in animals prone to develop intestinal inflammation.