Upregulation of CD94 on CD8(+)T Cells in Anterior Chamber-Associated Immune Deviation

BACKGROUND: CD8(+ )regulatory T cells (Treg) have been considered to be involved in a model of ocular-induced tolerance, known as anterior chamber-associated immune deviation (ACAID). The phenotype and characteristics of CD8(+)Treg in ACAID remain only poorly understood. Recent studies have reported that the CD94-Qa-1 system is implicated in the induction of ACAID CD8(+)Treg, but the functions and characteristics of CD8(+)CD94(+)T cells remain unclear. RESULTS: Both mRNA and protein of CD94 and NKG2A were markedly up-regulated on splenic CD8(+)T cells of ACAID mice compared with controls. Flow cytometric analysis showed that very few CD8(+)CD94(+)T cells express granzyme B, perforin and Foxp3. CD8(+)CD94(+)T cells, but not CD8(+)CD94(-)T cells, magnetically isolated from the spleens of ACAID mice, produced large amounts of TGF-beta1 and exhibited suppressive activity in vitro. Neutralization of TGF-beta1 caused reversal of suppression mediated by CD8(+)CD94(+)T cells. CONCLUSION: CD8(+)CD94(+)T cells from ACAID mice exhibited suppressive activity in association with enhanced expression of TGF-beta1, suggesting that CD8(+)Treg are mainly distributed in CD94(+)T cell subpopulations.