The lack of, or low level, response of the immune system towards an antigen, especially a tolerogen.
Immune tolerance that occurs under normal conditions is during pregnancy when the fetus and the placenta must be tolerated by the maternal immune system.
Immune tolerance may also be induced, for example during organ transplantation when the immune system must be forced to become unresponsive in order to accept an organ from another individual.
Word origin: immune + tolerance.
Variant: immunological tolerance