A paradoxical role of APCs in the induction of intravenous tolerance in experimental autoimmune encephalomyelitis

The central role of T cells in the induction of tolerance to autoantigens has been well documented. However, the role of antigen-presenting cells (APCs) in this process is not yet fully understood. To better understand the contribution of APCs in tolerance, we studied the interaction of purified APCs and CD4(+) T cells in a model of intravenous (i.v.) tolerance to experimental autoimmune encephalomyelitis (EAE). As expected, we found that T cells were tolerized to the autoantigen after i.v. injection. However, purified APCs obtained from MOG-i.v. -treated mice were paradoxically immuno-stimulatory, as they induced a non-specific Th1 -type response both in vitro and in vivo. We conclude that blocking such APC activation would enhance the effectiveness of tolerance induction. (C) 2005 Elsevier B.V All rights reserved.