Tryptophan catabolism, T cell responses & tissue transplantation: Innovative approaches to regulating immune responses

The method for tyrptophan catabolism, T cells and tissue transplantation which are useful in regulating and promoting adaptive immune responses in mammals are discussed. A hypothesis that cells expressing IDO inhibited T cells activation in response to the antigenic challenge due to local catabolism of the essential amino acid tryptophan was proposed. A model showing that T cells are sensitive to the amount of free tryptophan available during a critical period following antigen simulation was also proposed. It was shown that the cells transfected to express IDO inhibit T cell responses in vitro and in vivo.