Alloantigen-induced specific immunological unresponsiveness

When the immune system encounters alloantigen it can respond in any one of a number of different ways. The choice that is made will take into account factors such as where, when and how the contact with the alloantigen takes place, as well as the environmental conditions that were ail at the time th e alloantigen is encountered. Alloantigen administration before transplanta tion either alone or in combination with therapeutic agents that modulate t he functional activity of the responding leucocytes can be a powerful way o f inducing specific unresponsiveness to alloantigens: in vivo. The molecula r mechanisms that influence the way the outcome of the immune response to a lloantigen develops, either activation or unresponsiveness to the triggerin g antigen, hold the key to our ability to manipulate the immune system effe ctively by exposing it to donor antigen for therapeutic purposes. This revi ew will focus on alloantigen-induced immunological unresponsiveness and how insights into the mechanisms of unresponsiveness have driven the developme nt of novel tolerance-induction strategies that show promise for translatio n into the clinic in the future.