Antigen presentation by epithelial cells induces anergic immunoregulatory CD45RO+ T cells and deletion of CD45RA+ T cells.

The immunoregulatory effects of alloantigen presentation by tissue parenchymal cells to resting peripheral blood CD4+ T cells was investigated. Coculture of CD45RO+ (memory) and CD45RA+ (naive) T lymphocytes with primary cultures of MHC class II-expressing epithelial cells rendered both populations of T cells hyporesponsive to a subsequent challenge by the same MHC molecule expressed on EBV-transformed lymphoblastoid B cell lines. However, the mechanisms responsible for the allospecific hyporesponsiveness were distinct. For the CD45RO+ T cells, responsiveness was restored by subsequent culture in the presence of IL-2; the addition of IL-2 had no effect on the reactivity of the CD45RA+ T cells. In contrast, the naive T cells were protected from the induction of nonresponsiveness by the presence of a neutralizing anti-CD95 Ab during the culture with thyroid follicular cells. In addition, the hyporesponsive CD45RO+ T cells effected linked suppression, in that they inhibited proliferation against a third-party DR alloantigen when the third-party alloantigen was coexpressed with the DR Ag against which hyporesponsiveness had been induced. These results suggest that recognition of Ag by T cells on tissue parenchymal cells plays an important role in the maintenance of peripheral T cell tolerance, inducing nonresponsiveness in naive and memory T cells by distinct mechanisms.