CD103 is a marker for alloantigen-induced regulatory CD8+ T cells

The alpha(E)beta(7) integrin CD103 may direct lymphocytes to its ligand E-cadherin. CD103 is expressed on T cells in lung and gut and on allograft-infiltrating T cells. Moreover, recent studies have documented expression of CD103 on CD4(+) regulatory T cells. Approximately 4% of circulating CD8(+) T cells bear the CD103 molecule. In this study, we show that the absence or presence of CD103 was a stable trait when purified CD103(-) and CD103(+)CD8(+) T cell subsets were stimulated with a combination of CD3 and CD28 mAbs. In contrast, allostimulation induced CD103 expression on similar to 25% of purified CD103(-)CD8(+) T cells. Expression of CD103 on alloreactive cells was found to be augmented by IL-4, IL-10, or TGF-beta and decreased by addition of IL-12 to MLCs. The alloantigen-induced CD103(+)CD8(+) T cell population appeared to be polyclonal and retained CD103 expression after restimulation. Markedly, in vitro-expanded CD103(+)CD8(+) T cells had low proliferative and cytotoxic capacity, yet produced considerable amounts of IL-10. Strikingly, they potently suppressed T cell proliferation in MLC via a cell-cell contact-dependent mechanism. Thus, human alloantigen-induced CD103(+)CD8(+) T cells possess functional features of regulatory T cells.