Immunity is the body’s ability to resist infection from pathogens. There are two types of immunity: innate and acquired. Innate immunity is the kind organisms are born with, and acquired immunity is the result of experiences in the past. Immunity occurs when the body produces antibodies against foreign substances, which recognize the infection and fight it. Passive immunity can be acquired through the natural process or through artificial methods. Both are important.
The word immunity comes from Latin immunitas, which referred to a legal status granted to certain city-states by Rome. Immunity provided them protection against paying tributes to Rome or imposing municipal duties. The word munis, which is Greek for “change”, is also used to describe immunity. In 1848, the Islamic physician Al-Razi described immunity in his A Treatise on Smallpox.
Passive immunity is not permanent; it only lasts a few weeks or months. Passive immunity develops with exposure to a foreign antigen. The immune system produces antibodies to protect the body from disease and helps fight off infection. Passive immunity is also available through vaccinations. Passive immunity is acquired during pregnancy, and includes IgG and IgA in the human milk. The immune system’s response to these vaccines is called adaptive immunity.
Passive immunity is similar to innate immunity, but it requires learning from exposure. Passive immunity is a lifelong, genetically encoded defense mechanism that enables the body to recognize and destroy foreign invaders. A healthy immune system produces many “self” antigens. Passive immunity is regulated, and suppressed immunity to harmless macromolecules is considered healthy. In other words, tolerance is a normal part of the immune system.