Immunity is the body’s self-defense mechanism to keep diseases at bay.
When this immunity is compromised or weakened, then the body is susceptible to diseases and infections.
Immunity is executed by two components in the body.
One is the anti-body component which neutralizes foreign bodies from further actions in the body.
The other is cellular component which eats up and destroys the foreign organism.
So the way to prevent diseases from microorganisms is to build up immunity. There are three types of immunity
3 Types of Immunity
- Immunity based on response/ specificity
- Based on the components involved
- Based on the location of immunity.
Immunity based on specificity is again of two types.
- Innate immunity (Natural immunity)
- Acquired immunity (Adaptive immunity)
Natural Immunity: This is the immunity present from birth of an individual or animal. It is a non-specific type of defense with different types of barriers to prevent entry of pathogens into the body. This innate immunity has 4 four important barriers for immunity like
- Physical barrier
- Physiological barrier
- Cellular barriers
- Cytokine barrier.
When a new infection enters the body, the body produces a complex set of immune reaction to neutralize the foreign body. This immunity is strong and prevents many infections during childhood. See more details on examples of innate immunity.
Adaptive immunity: This is the immunity not present from the birth but develops after a first attack. For example a person who contracts chickenpox during childhood never gets it again. This is because the body has developed memory for that foreign infection and when it re-enters, there is quick response to neutralize and destroy it. This is developed immunity toward older infections is adaptive immunity.
Acquired immunity: This sounds similar to adaptive immunity. But it is acquired intentionally by use of vaccines in humans. This immunity is very specific for an infection or even to specific strain of infection. This immunity can last for few years to even lifetime.
Based on the components involved; Immunity is produced by two components of the body.
- Humoral immunity
- Cellular immunity
Humoral immunity is one where self-defense if done by antibodies. I.e. no cellular components are not involved. The end result is neutralization of foreign bodies.
Cellular immunity: Here the immune defense is by production of cellular components like macrophages, lymphocytes etc. The end result is destruction of foreign bodies.
Based on immune response:
This is based on where the immune response happens. This is of two types like Primary response and secondary response.
Primary response is slow or delayed in producing the antibodies. Also it is short lived.
Secondary response is a swift response and triggers a violent attack on the infectious pathogens or toxins.