Identification of the genes specifically expressed in orally tolerized T cells.

Oral tolerance is the systemic immunological unresponsiveness that occurs after feeding protein antigens. Its physiological role is thought to be the prevention of hypersensitivity to food antigens, and its therapeutic use to treat inflammatory diseases has been suggested. Although it has been shown that CD4(+) T cells mediate oral tolerance, the precise molecular mechanisms remain unclear. In the present study, we employed suppression subtractive hybridization and identified 10 genes specifically expressed in orally tolerized T cells. These included genes that were interesting in terms of their putative functions in the negative regulation of T cell activation, e.g. Culin 1, LAX, and Zfhx1b, as well as four genes that encoded unknown proteins. We further investigated the expression of these genes in hyporesponsive T cells induced in vitro (in vitro anergized T cells). We found that six of the 10 genes were highly expressed in these cells, and kinetic studies suggested that one was associated with the induction of anergy, while the other five were associated with the maintenance of anergy. The remaining 4 genes that were not expressed in in vitro anergized T cells are also of interest as they may play a specific role in in vivo T cell tolerance. Functional analysis of these genes should help to understand the complex mechanisms underlying the induction and maintenance of oral tolerance, and moreover, in vivo immune tolerance in general.