Our human body is continuously exposed to microorganisms that may or may not be infectious. Millions of microorganisms exist in our body that includes our mouth, eyes, ears, and the other various part of our body.
But in the same way, our body is also exposed to disease-causing microorganisms such as viruses, bacteria, fungi, protozoans, etc. So in order to keep us healthy, there is a certain process that our body undergoes in order to defend ourselves from such microorganisms, this is done by our immune system. The branch of science that deals with the components of the immune system are called Immunology.


It is the ability of an organism to fight against disease-causing agents.
It is further divided into two categories :

  1. Innate immunity.
  2. Acquired immunity.


It is a non-specific type of immunity that includes all the defense elements with which an individual is born. It is present at the time of birth and is genetic i.e, it is passed down genetically from parents to children.
This includes skin, mucous membranes, and blood cells along with the white blood cell which forms an important component of innate immunity.

The different types of barriers to innate immunity are :

1) Physical barrier: This includes skin and mucous membrane

2) Physiological barrier: This comprises hydrochloric acid, bile, cerum, lysozyme, and our body temperature.

3) Cellular barrier: Certain types of cells called leucocytes(WBC), neutrophils and monocytes, natural killer cells (lymphocyte) as well as macrophages constitutes this barrier.

4) Cytokine barrier: There are certain cells which once infected by a virus, release a glycoprotein called interferons (IFNs). This causes the nearby cell to get alert, as it is a signal which basically says pathogens have been entered and have infected it.

5) Inflammatory barrier: This is a type of barrier that causes redness, swelling, pain, and the production of heat from the infected tissue.


This type of immunity is found only in vertebrates. It is also called adaptive or specific immunity. It enhances the protection of the innate immunity as it is generated in response to the exposure of pathogens.

These are further divided into two groups:

1) Active immunity.

2) Passive immunity.


It involves the active functioning of an individual’s own immune system, which leads to the synthesis of antibodies.

Types of active immunity:

1) Natural active immunity: Natural infection by a pathogen generates antibodies and specialized lymphocytes.

2) Artificial active immunity: Vaccines are administrated to the body which generates antibodies.


In this case of immunity, the antibodies from one individual are passed into another individual. It also gives immediate protection. But this type of immunity is short-lived, generally lasts for only a few weeks.

Types of passive immunity:

1) Natural passive immunity: It is gained naturally, for example, antibodies from a mother can cross the placenta and enter her foetus.

2) Artificial passive immunity: Here the antibodies formed in one individual are extracted and are then injected into the blood of another individual.


We have an immune system in our body that help us fight against the disease-causing microorganisms or pathogen. Some Immunity may be passed to us during our birth and can also be passed to our next generation, this type of immunity is called innate immunity. While the immunity that is acquired after birth that has the ability to recognize and selectively eliminate a certain specific type of pathogens is called Acquired immunity.

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