Dominant regulation - A common mechanism of monoclonal antibody induced tolerance?

Transplantation tolerance can be induced by a range of agents that block T cell/antigen-presenting cell (APC) interactions known to be important for i nitiation of the adaptive immune response. Tolerance so induced has been sh own to have a regulatory phenotype dependent on CD4(+) cells. This was firs t observed with nonlytic anti-CD4 antibodies, and was recently demonstrated following other therapeutic approaches. Dominant tolerance also plays a ro le in natural regulation of the immune response, functioning to prevent aut oaggressive cells mediating self-destruction. The mechanism by which domina nt tolerance is established and maintained remains unclear, and the reporte d characteristics of regulatory cells in different experimental models vary widely. Here we review the evidence for potential mechanisms involved and propose that there is a common pathway by which dominant tolerance is media ted.