In this article, we will try to examine the performance and improvement of the immune system in terms of gender segregation, infant and adult life, including pregnancy, ending with the decline in old age. A picture emerges of a child born with an immature, innate and adaptive immune system, which matures and acquires memory as he or she grows. It then goes into decline in old age. These changes are considered in addition to the risks of various types of infection, autoimmune diseases, sex, and various stages of life of individuals.