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Last Updated : 16 Nov, 2023
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Immunology is the study of the immune system that consists of several types of immunity such as cell-mediated immunity and humoral immunity, diseases related to the immune system, and the physiological and biological functioning of the immune system. Edward Jenner is known as the “father of Immunology” because he developed first the smallpox vaccine in 1796.


Definition of Immunology

In biomedical research, immunology is the field that studies how an organism responds to an antigen and distinguishes between its own and other substances. It comprises the defensive systems of the organism that aid in fending off its vulnerability to foreign substances.

What is Immune System?

Through a variety of defense mechanisms, the immune system serves as the body’s defense system, defending our tissues, cells, and organs against pathogens that invade them. The immune system consists of such types of cells that aid in identifying and eliminating foreign antigens, such as pathogenic bacteria, fungi, and viruses that cause illness.

Weakening of the immune system results in the elevation of pathogen attacks and the severity of the disease. So Strong immune system is crucial for our body to limit infection. When normal tissue is incorrectly seen as diseased by the immune system, it results in a needless attack that causes painful and occasionally severe symptoms in autoimmune disorders and allergies.

Immune system is composed of many components such as:

  1. Leukocytes (WBC)
  2. Lymphatic system
  3. Bone marrow
  4. Thymus
  5. Spleen
  6. Adenoids, tonsils, and appendix


These are also known as white blood cells, and they are present in blood as well as lymphatic fluid. WBCs helps in fighting the antigen such as pathogens. WBCs are of two types of granulocytes and non-granulocytes.

Lymphatic System

WBCs are present in lymphoid system from there they travel to different organs via lymphatic vessels.

These lymphoid organs include:

  • Spleen: Spleen is the hub of immune cells, where they work, and it is located at upper left side of abdomen.
  • Thymus: Thymus is a gland where matured WBCs formed and known as lymphocytes mature, It is located below the breastbone.
  • Bone marrow: – It is a soft red or yellow colour tissue located in the centre of the bone which is responsible for haematopoiesis i.e. formation of blood cells.
  • Lymph nodes: – These are tiny glands that resemble beans that are found all over the body, but particularly in the neck, crotch, and stomach.
  • Adenoids: – This the gland located in high throat and behind the nose.
  • Tonsils: – These are associated with mucosal associated lymphoid system that plays a crucial role in defence against pathogens. These are located back side of the throat.
  • Appendix: – These are associated with mucosal associated lymphoid system that plays a crucial role in defence against pathogens. It is gut associative lymphoid tissue.

Cells of Immune System

There are several white blood cells which plays a important role in immune system

White blood cells are of two types:

  • Granulocytes: Thes WBCs have granules in their cell cytoplasm
    • Neutrophils: These are the part of innate immune system and accounts for 40 – 70 %
    • Eosinophils: These cells work against multicellular parasites and infection causing pathogens.
    • Basophils: They have anti cancerous property and responsible for inflammatory reaction certain skin allergies.
  • Agranulocytes: These WBCs don’t have granules in their cytoplasm.
    • Monocytes: They are largest agranulocyte and are the part of innate immune system. These cells further differentiated into: –
  • Macrophages: These cells are known as phagocytic cells which plays an important role in antigen engulfment known as phagocytosis.
  • Dendritic cells: These are antigen presenting cells (APCs) which process the cell and present it to the receptors present of T cell for further processing.


These cells play crucial roles in immune system and consists of

  • T and B cells: The two main biological components of the adaptive immune response are B lymphocytes (derived from bone marrow or bursa) and T cells (derived from the thymus). B cells are mostly in charge of humoral immunity, while T cells are involved in cell-mediated immunity (relating to antibodies). Antigen presentation is the mechanism by which T cells and B cells identify certain “non-self” antigens.
  • Natural killer cells: Natural killer cells are a subset of cytotoxic lymphocytes that are essential to the innate immune system. They comprise 5–20 percent of the rapidly growing family of innate lymphoid cells (ILC). NK cells react quickly to internal pathogens, such as viruses, and to newly formed tumours.
  • Innate lymphoid cells: The most recently identified class of innate immune cells is called innate lymphoid cells (ILCs), and they are descended from common lymphoid progenitors (CLPs). ILCs support immunity by regulating both innate and adaptive immune cells and secreting signalling molecules in response to pathogenic tissue injury.

There are some other cells also include:

  • Mast cells: A mast cell is a resident cell of connective tissue that is also referred to as a mastocyte or labrocyte. It is composed of many granules that are high in heparin and histamine. Mast cells are well recognised for their involvement in allergy and anaphylaxis, but they also have a significant defensive function.

Types of Immune System

There are basically two types of immune system that includes: –

  1. Innate immune system that you have by birth.
  2. Adaptive immune system which develops as you get in touch with certain foreign particles.

Innate Immune System

This is the quick response system for your child. If it discovers an intruder, it reacts first. It consists of

  • Mucous membrane lining the gastrointestinal
  • Genitourinary
  • Respiratory systems
  • Skin
  • Cornea of the eye


All of these provide tangible barriers to shield your child’s body. They offer defence against pathogenic bacteria, parasites (like worms), or cells (such as cancer). One inherits the innate immune system. It starts working as soon as your child is born. This immune system’s cells envelop and cover the intruder. Inside the immune system cells, the intruder is eliminated (called phagocytes).

Adaptive or Acquired Immune System

The innate system assists the acquired immune system in producing specialised proteins, or antibodies, that shield your body against a particular intruder. After the body is exposed to the invader, cells known as B lymphocytes produce these antibodies. The child’s body retains the antibodies. Antibodies might take many days to develop. However, the immune system will identify the intruder and mount a defence after the initial encounter. Your child’s acquired immune system develops throughout time. Immunizations prepare your child’s body to produce antibodies that will shield them from dangerous illnesses.


There are two different kinds of adaptive responses:

  • Cell-mediated immunity, which is mediated by T cells.
  • Humoral immunity, which is mediated by antibodies produced by B lymphocytes.

Disorders of Immune System

The immune system can malfunction in several ways. Immune dysfunction types may be divided into three groups:

1.Autoimmune disorders

These are the immune disorders in which our own immune cells mistakenly start attacking the own body cells. These disorders include: –

  • Rheumatoid arthritis
  • Type 1 diabetes
  • Lupus antigen
  • Multiple sclerosis
  • Psoriasis
  • Chron’s diseases
  • Alopecia areata

2. Primary Immune Diseases

  • BENTA disease
  • Caspase Eight
  • APS-1
  • Autoimmune lymphoproliferative syndrome

3. Immunodeficiency

  • Severe combined immunodeficiency (SCID)

4. Others immune disorders includes:

  • Ataxia telangiectasia
  • Asthma
  • Burkitt lymphoma
  • DiGeorge syndrome

Symptoms of Immune dysfunction

These are the common symptoms of all immunlogical disorders: –

  • Recurrent pneumonia, skin and ear infection, sinus and bronchitis
  • Low platelet count
  • Anemia
  • Inflammation or internal organs
  • Loss of appetite, nausea
  • Recurrent fever
  • Pain in joints
  • Swelling of joints
  • Abdominal pain
  • Swelling of glands

Techniques of Immunology

There are various techniques which are used in immunology laboratory to find out antigen, antibody, immune cells etc. These techniques includes: –

  1. Enzyme linked immunosorbent assay (ELISA)
  2. Immunohistochemistry
  3. Serology
  4. Flow cytometery
  5. Immunoassay
  6. Radioimmunoassay
  7. Immunofluorescence
  8. Immunoprecipitation
  9. Immunoelectrophoresis
  10. Immunodiffusion
  11. Complement fixation test (CFT)
  12. Immunochemical technique

Applications of Immunology

Immunology is used in many medical specialties, including: –

  • Oncology
  • Transplantation
  • Psychiatry
  • Rheumatology
  • Endocrinology
  • Parasitology
  • Bacteriology
  • Virology

FAQ’ s – Immunology

1. What is Immune Disorder in Immunology?

An immune disorder is a malfunction of the immune system, which can be classified based on the affected components, overactivity, underactivity, and whether it’s congenital or acquired.

2. What are the Three main Types of Immunological Disorders?

Three prevalent autoimmune diseases include Type 1 diabetes, where the immune system targets pancreatic insulin-producing cells; Rheumatoid arthritis, leading to joint swelling and deformities; and Lupus, which affects various body tissues, such as the lungs, kidneys, and skin.

3. What is Immunology and Types of Immunology?

Immunology, essential in medical and biological sciences, delves into the immune system’s complex operations, our defense against infections. Malfunctions can result in conditions like autoimmunity, allergies, and cancer.

4. What is Immune System?

The immune system, a intricate network of organs, cells, and proteins, safeguards the body from infections while preserving its own cells. It retains a memory of conquered germs, enabling rapid response upon re-entry into the body.

5. Why is Immunology Important?

Immunology, a critical field in medicine and biology, examines the immune system’s role in safeguarding the body against infections. When the immune system falters, it can lead to diseases like autoimmunity, allergies, and cancer.

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