[Biology Class Notes] on Immunity System Pdf for EXAM

Children, both infants and toddlers tend to fall ill more often and are more prone to infections as they do not have a fully developed immune system, compared to adults. Likewise, as people grow old, their immune system weakens and makes things worse.

Every person has a different immune system and it varies with age, lifestyle and there are many factors which affect the immune system of a human being. 

The Immune System consists of different types of cells and molecules, which protect our body against pathogens. Pathogens are defined as everything from parasites to fungi, bacteria, viruses and haptens. Haptens are molecules that may cause an immune response when they come in contact with a protein. All these cells and molecules are divided equally  in all the tissues of the body as well as lymphoid organs, which eliminate or prevent microbial infections to decrease the growth of tumours and start the repairing process of damaged tissues.

Types of Immune System

Immune System fights against microbes and is divided into different types of reactions. The three types of immunity are:

Innate Immunity

We all are born with innate (or natural) immunity, a type of natural protection.

The immunity that is attached to us by birth is defined as the Innate Immunity. It refers to the defence system of the body which helps a person to fight diseases off. 

For example, the skin, the barrier of the human body functions by protecting the entry of germs and other disease-causing pathogens.

Adaptive Immunity

When an individual acquires immunity after birth that is termed as adaptive or acquired immunity. Adaptive immunity develops throughout our lives. We acquire an immunity when we are exposed to infectious diseases and allergies or when we are immunized against them with vaccines, that is termed as adaptive immunity. 

Passive Immunity

This is a kind of immunity developed by antibodies that are produced outside the body. This immunity lasts for a short time. For example, the antibodies that are present in a mother’s breast milk gives a baby with temporary immunity against the diseases.

Active Immunity

Active immunity is a type of adaptive immunity, which is developed due to the production of antibodies in one’s own body. This type of immunity occurs when we are in contact with the pathogen or its antigen. When the active immunity 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..

What are the Parts of the Immune System?

The main parts where the immune system can be found are –

• Spleen.

• Thymus.

• Antibodies.

• Bone marrow.

• White blood cells.

• Lymphatic system.

• Complement system.

Disorders of the Immune System

Some of the common disorders caused by a poor immune system include:

• Allergic diseases – These are the diseases which have symptoms which include hay fever, sinus disease, asthma, hives, dermatitis and eczema.

• Autoimmune diseases – These include multiple sclerosis, autoimmune thyroid disease, type 1 diabetes, systemic lupus erythematosus, rheumatoid arthritis and systemic vasculitis.

• There are immunodeficiencies, which are inherited from a parent to the child. These conditions include primary immunodeficiency diseases such as x-linked severe combined immunodeficiency (SCID), complement deficiencies, common variable immunodeficiency (CVID), etc