What Is the Immunity System and How It Works
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
FAQs on Immunity System in Humans Structure and Role
1. What is the immune system?
The immune system is the body’s defense system that protects against infections and harmful foreign substances. It is made up of specialized cells, tissues, and organs that work together to identify and destroy pathogens such as bacteria, viruses, fungi, and parasites.
- Includes white blood cells (leukocytes)
- Involves organs like the lymph nodes, spleen, and bone marrow
- Detects and responds to foreign molecules called antigens
2. What are the main functions of the immune system?
The main function of the immune system is to recognize and eliminate pathogens while protecting the body from disease. It performs several key roles:
- Identifies foreign antigens
- Destroys pathogens using immune cells and antibodies
- Remembers past infections through immunological memory
- Removes damaged or abnormal cells
3. What is the difference between innate and adaptive immunity?
The difference between innate immunity and adaptive immunity is that innate immunity provides immediate, non-specific defense, while adaptive immunity is specific and develops memory.
- Innate immunity: Present at birth, includes barriers like skin and cells such as macrophages.
- Adaptive immunity: Develops after exposure, involves B cells and T cells.
- Adaptive responses are slower initially but faster upon re-exposure.
4. How does the immune response work step by step?
The immune response works by recognizing, attacking, and remembering pathogens in a coordinated sequence.
- Recognition: Immune cells detect foreign antigens.
- Activation: White blood cells become activated and multiply.
- Response: Pathogens are destroyed by phagocytes or antibodies.
- Memory formation: Memory B and T cells remain for faster future responses.
5. What are antibodies and what do they do?
Antibodies are Y-shaped proteins produced by B lymphocytes that specifically bind to antigens to neutralize pathogens. They function by:
- Blocking viruses from entering cells
- Marking pathogens for destruction (opsonization)
- Activating the complement system
6. What are white blood cells and why are they important?
White blood cells (leukocytes) are immune cells that defend the body against infection and foreign invaders. They are important because they detect and eliminate pathogens. Major types include:
- Neutrophils – engulf bacteria
- Lymphocytes – include B cells and T cells
- Monocytes/Macrophages – perform phagocytosis
- Eosinophils and basophils – involved in allergic responses
7. What is an antigen?
An antigen is any foreign substance that triggers an immune response in the body. Antigens are usually proteins or polysaccharides found on the surface of pathogens such as bacteria and viruses.
- Recognized as non-self by immune cells
- Bind specifically to antibodies or T cell receptors
- Stimulate production of targeted immune responses
8. What is immunological memory?
Immunological memory is the ability of the adaptive immune system to respond faster and more effectively to a previously encountered pathogen. It is formed after the first infection or vaccination.
- Involves memory B cells and memory T cells
- Provides long-term protection
- Basis of vaccination
9. How do vaccines work with the immune system?
Vaccines work by stimulating the adaptive immune system to produce immunity without causing the actual disease. They contain weakened, inactivated, or fragments of pathogens.
- Introduce harmless antigens
- Trigger antibody production
- Create memory cells for future protection
10. What is an autoimmune disease?
An autoimmune disease is a condition in which the immune system mistakenly attacks the body’s own healthy cells. This occurs when self-antigens are wrongly identified as foreign.
- Examples include rheumatoid arthritis and type 1 diabetes
- Leads to chronic inflammation and tissue damage
- Often involves malfunction of immune regulation
