Answer:
Immunity is the balanced state of multicellular organisms having adequate biological defenses to fight infection, disease, or another unwanted biological invasion, while having adequate tolerance to avoid allergy and autoimmune diseases. Each part of the immune system has a unique function. Also, the immune system is responsible for down-regulating immune responses against external harmless triggers such as food, or against the bodies' tissue. Active immunization is the induction of immunity after exposure to an antigen. Antibodies are created by the recipient and may be stored permanently. Naturally acquired active immunity occurs when the person is exposed to a live pathogen, develops the disease, and becomes immune as a result of the primary immune response. And passive immunity is the transfer of active humoral immunity of ready-made antibodies. Passive immunity can occur naturally when maternal antibodies are transferred to the fetus through the placenta. Passive immunity refers to the transfer of antibodies from one individual to another.