Immune System - Active and passive immunity

It is known to all of us that our body will defend an intruder or any foreign material by deterring them from entering and multiplying. The immune system of our body is responsible for this defense mechanism. Let us explore more about how immune system works in this page.

Types of Immunity

Immunity is defined as the property or ability of a body to resist the pathogens or foreign bodies that cause diseases. The immune system is of two types

  1. Innate or inborn immune system
  2. Acquired or adaptive immune system.

Acquired or adaptive immunity is further classified into two, Active Immunity and Passive Immunity. Both the active and passive immunity is essential for protecting our body.

Acquired immune system


Acquired Immune system

Acquired Immune system

Active Immunity

In case of the acquired or adaptive immune system, the body remembers the pathogens it has encountered in the past. This is a direct result of the active immune system. Active immunity occurs when we are in contact with the pathogen or its antigen. Antigens stand for antibody generator. It is with the help of antigens released by the pathogen that our body tackles the pathogen. So what our body does is, it starts producing antibodies to attack the pathogen based on its antigen. When this happens for the first time, it is called a primary response. Once a body experiences a pathogen for the first time, it keeps a few of the antibodies that attacked the pathogen just in case it attacks for the second time. This is known as natural active immunity.

Active Immunity

Injecting pathogenic microbes into our body deliberately incites a similar response from the body but since it is caused artificially, it is known as artificial active immunity. The injection of microbes to the body in order to become immune from it is known as the process of immunization.

Passive Immunity

The primary response by the body to a pathogen it encounters for the first time is rather feeble, so the first encounter is always a little harsh on the body. What if we could immunize everyone without the need for them ever getting sick? Biotechnology has grown tremendously in the last decade or two and now we are capable of manufacturing antibodies for diseases. These ready-made antibodies protect the body even if the body hasn’t yet experienced a primary response. While active immunity may protect us from a disease for a lifetime, passive immunity is the more short term. Passive immunity develops immediately and our body could begin its attack on the pathogen right away. There are two types of passive immunity; natural passive immunity and artificial passive immunity.

Passive Immunity

Do you know why it is essential for a newborn infant to consume its mother’s milk? The mother’s body secretes a yellowish fluid in the initial days of lactation. This fluid is known as the colostrum and it has abundant antibodies to protect the infant till it can develop its own immune system. Other than this, the newborn infant also receives antibodies from the mother, through the placenta during pregnancy. These are examples of natural passive immunity. Artificial passive immunity occurs when the antibodies specific for a pathogen are transferred to an individual who is not immune to that pathogen. This way he gains some immunity without encountering the pathogen.

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Practise This Question

What is the function of secretory protein in IgA?