Types of Immunity: Innate and Acquired

In this article we will discuss about innate and acquired immunity.

Innate Immunity:

It refers to all the defence elements with which an individual is born and always available to protect the body. It is a non-specific type of defence system.

(i) It is present from the time of birth and inherited from parents.

(ii) It consists of four types of barrier system that prevent the entry of pathogen or foreign element in to the body.

Types of Barrier in Immune System:

Various types of barriers in immune system are as follows:

(i) Physical Barrier:

Skin is the first line of mucous coating on defence. It prevents the entry of the pathogens of the body. Mucous coating on the epithelium lining the respiratory, gastrointestinal and urogenital tracts also help in trapping microbes.

(ii) Physiological Barrier:

Acid in the stomach, saliva in the mouth, tears from the eyes, etc., prevent the entry of microbes.

(iii) Cellular Barrier:

Special types of cells in our body, which kill the disease causing agents. Example are WBCs, Lymphocytes, Polymorpho Nuclear Leukocytes (PMNL—neutrophils, monocytes, macrophages, etc.

(iv) Cytokine Barrier:

Cells which are virus-infected, release types of protein called interferon’s. Interferons protect the uninfected cells from further infection.

Acquired Immunity:

It is pathogen specific and is not present from the birth and develops during an individual’s lifetime.

This type of immunity is acquired after the birth, either by contracting the disease or by vaccination.

It has the following characters given below:

1. Specificity:

It has the ability to distinguish many different foreign molecules accordingly.

2. Memory:

It is a unique feature, which helps in producing an intensive response when the pathogen attacks the second time.

Types of Acquired Immunity:

Acquired immunity can also be classified as:

(i) Active Immunity:

It is the immunity developed by the body, when it is exposed to the antigens. Antibodies are produced by the body in this case.

Introduction of pathogens or microbes either during immunisation or by any infection induce active immunity. It is slow but long lasting process and has no side effects.

Few examples of this immunity are as follows:

(a) Immunity developed by vaccination

(b) Immunity developed during natural infection

(ii) Passive Immunity:

It occurs when antibodies are directly given into the body. It is used when the immune response has to be faster.

Some examples of passive immunity are:

(a) Antibodies received by foetus from mother through placenta.

(b) Antibodies in the colostrum (IgA rich), i.e., yellowish fluid secreted by mother during the initial days of lactation.

(c) It is fast but lasts only for few days.