Before revision:  Our main purpose was to compare different theoretical models of the adaptive immune system and self--nonself discrimination: the ones that are described by well-known textbooks, and a novel one developed by our research group. Our theoretical model emphasizes the hypothesis that the immune system of a fetus can primarily learn what self is but unable to prepare itself for the huge, unknown variety of nonself. The simulation begins after conception, by developing the immune system from scratch and learning the set of self antigens. The simulation ends several months after births when a more-or-less stationary state of the immune system has been established. We investigate how the immune system can recognize and fight against a primary infection. We also investigate that under what conditions can an immune memory be created that results in a more effective immune response to a repeated infection.
After revision:  We investigate under what conditions can an immune memory be created that results in a more effective immune response to a repeated infection.