Identification of CD3(+)CD4(-)CD8(-)T cells as potential regulatory cells in an experimental murine model of graft vs. host skin disease (GvHD)

We have developed K14-mOVA transgenic (Tg) mice that express membrane-associated ovalbumin (mOVA) under the control of a K14 promoter as well as double Tg mice by crossing them with OT-I mice that have a T cell receptor (TCR) recognizing OVA peptide. When injected with CD8(+) OT-I cells, K14-mOVATg mice develop graft-vs-host disease (GvHD), whereas double Tg mice are protected. This suggests that, in double Tg mice, regulatory mechanisms may prevent infused OT-I cells from inducing GvHD. We demonstrated that, after adoptive transfer, TCRαβ(+)CD3(+)CD4(-)CD8(-)NK1.1(-) double negative (DN) T cells are increased in the peripheral lymphoid organs and skin of double Tg mice and exhibit a Vα2(+)Vβ5(+)TCR that is the same TCR specificity as OT-I cells. These DN T cells isolated from tolerant double Tg mice proliferated in response to OVA peptide and produced IFN-γ in the presence of IL-2. These cells could also suppress the proliferation of OT-I cells and were able to specifically kill activated OT-I cells through Fas/Fas ligand interaction. These findings suggest that DN T cells that accumulate in double Tg mice have regulatory functions and may play a role in the maintenance of peripheral tolerance in vivo.