Difference Between Natural Immunity And Active Immunity And Passive Immunity
The invisible battle goes on day and night. There are many enemies lurking about, waiting to attack. On guard is a tireless army of defenders, posed and ready to fight. These defenders are part of the immune system—a remarkable system that protects the body from harmful invasions by foreign substances and disease-causing organisms.
The body’s ability to protect and defend itself against a foreign enemy agent is called immunity. There are several types of immunity. Natural immunity is a type of general inherited protection. A person is born with natural immunity, and it is species specific—for example, people do not get cat distemper and cats do not get human colds. Active immunity is the protection a person develops during his or her lifetime as the result of actually having been immunized against a disease. One way this can be done is by using vaccines to help an individual develop active immunity. Active immunity is long-lived and may even last a person’s lifetime. Passive immunity is a temporary form of immunity that is borrowed from another source. It is short-lived, only lasting a matter of weeks. A baby receives passive immunity from its mother before it is born and after it is born from the mother’s milk. Passive immunity protects the baby until it is old enough to have its “baby shots.” Then the baby will build its own active immunity.
When the immune system sets up an attack against a foreign agent, it must first recognize which cells belong to the body and which do not so that it can selectively destroy the invader while protecting the healthy body cells. The immune system can tell the difference between what is self (the body’s cells and tissue) from something that is foreign because of the chemical labels that appear on the outside surface of all body cells. The cells in a person’s body have chemical self labels; each person has their own unique set of self labels. Invading agents also have chemical labels; each invading agent has foreign antigen labels.
Each foreign antigen has its own chemical configuration—just as each person has a unique set of human fingerprints. Because each foreign antigen has its own unique set of chemical fingerprints, the immune system is able to recognize the difference between foreign agents and develop a separate defense against each.