Immune privilege is a unique strategy developed in several internal organs that can prevent the development of immune attack against these vital organs. One critical mechanism of immune privilege is utilization of Fas/FasL-mediated apoptosis to delete the invading T cells at the immune privilege sites. In this article, we describe the development and application of a unique cell-gene therapy to correct defective FasL-mediated apoptosis and autoimmune disease in autoimmune mice. This cell-gene therapy strategy using antigen-presenting cells (APCs) to express FasL is not only a therapeutic tool, but also has allowed us to understand the complexity of T cell regulation and the concept of eliminating T cells in the spleen, lymph node, or elsewhere in vivo to regulate the homeostasis of the peripheral T cell response. In this regard, the FasL-expressing APCs can be considered as circulating and regulatable immune privilege sites. Our studies provide substantial evidence that FasL-expressing APCs can be introduced exogenously without liver toxicity to eliminate infiltrating T cells and prevent the development of immune attack in lung, liver, kidney, joint, and salivary gland. Therefore, given the hazardous potential of persistent T cell invasion at the local inflammatory site, it is tempting to speculate that such an endogenous control mechanism occurs normally in vivo to limit a chronic T cell inflammatory response.