What is Immunity | Types, Definitions, Immune system

Hello friends, today we will talk about immunity, what is immunity? If you know about it well step by step, then let’s start.

What are immunity Definitions?

Immunity –

Any living being has a body, it protects itself in many ways. The human body struggles with almost all kinds of toxins and microbes that try to damage the organs and tissues of the body. This type of ability is called Immunity.

In other words, the ability to fight diseases is called immunity.

What is immunity?
What is immunity?

What is Acquired immunity?

Most immunity is activated by a specific type of immune system. Which produces antibodies and activates lymphocytes. They attack and kill specific bacteria and toxins. This type of immunity is called acquired immunity.

What innate immunity?

But an additional part of immunity is driven by normal processes and not by the operation of specific pathogenic organisms. This is called Innate immunity. Under this come the following.

  • Phagocytosis – feeding on bacteria and other intruders that feed on white blood cells and cells of the tissue macrophage system.
  • The bacteria ingested while eating food are destroyed by the acid and digestive enzymes released from the stomach.
  • Acts to prevent bacteria from entering the skin.
  • Such chemicals are present in the blood and destroy foreign or foreign organisms and toxins.

Some of these are as follows –


  • It is a mucolytic polysaccharide that attacks and kills bacteria.

Basic Polypeptides –

  • This polypeptide reacts with certain types of Gram-positive bacteria and inactivates them.

Complement Complex –

  • A mechanism of about 20 proteins that can be activated in a variety of ways to destroy bacteria.

Natural Killer Lymphocyte –

  • They can identify and eliminate various cells, tumor cells, and some infected cells.
  • In this way, natural immunity makes the human body resistant to diseases such as – infection of paralytic viruses in animals – cattle plague, hog cholera, distemper, etc.

Cells of the Immune System –

The important mechanisms of the immune system by which it acts are carried out by different types of cells. All cells of the immune system develop from the same type of pluripotent cells in the bone marrow of adults. It develops from stem cells in two chains –

Lymphoid lineage – It produces different types of lymphocytes.

Myeloid Lineage – This produces phagocytes and other cells.

Lymphoid lineage: – Two types of lymphocytes are produced in this chain.

  1. β Lymphocytes –
  2. T Lymphocytes

In addition to β- and T-lymphocytes, there is a third type of cell called null cells, which are also formed. Null cells are completely different from β and T-lymphocytes because they do not contain β and T-cell markers. It is known that the null cells are again divided into two classes –

Killer cells (k-cells) – These are killer cells dependent on antibodies.

Natural Killer Cells (Nk-Cells) – These are not dependent on antibodies.

Myeloid Lineage – Two types of cells develop in this line.

  • Monocytes –
  • Polymorphonuclear leucocytes (PMN)

Monocytes are further differentiated into macrophages while the following are under polymorphonuclear leukocytes –

  • Eosinophils
  • Basophils
  • Neutrophils

Apart from the above-mentioned cells, many types of accessory cells also develop. which is the following –

Antigen-presenting cells –

A special group of antigen-administering cells for β- and T-cells are called antigen-presenting cells.

Platelets –

The cells that conduct blood clotting, as well as immune experience, are called platelets.

Mast cells – These cells are similar to basophils.

Origin of Cells of the Immune System –

In the later embryonic stage, hemopoiesis occurs only in the red bone marrow and liver, and in the early stages, it occurs in the yolk sac.

The most fundamental cell in the red bone marrow is the pluripotent stem cells. From which dedicated stem cells are formed, one type of dedicated cell gives rise to the myeloid chain (granulocytes, erythrocytes, platelets, and monocytes) and the other type gives rise to lymphocytes (both types β and T).

Stem cells –

Stem cells are also called hemocytoblasts. These are integrated cells and are incapable of resistance. These cells are of the titan type. Which have the embryonic potential to develop into all types of blood cells.

Stem cells are large in shape with pyrinophilic cytoplasmic margins and leptochromatic nuclei. These colonies are capable of multiplying and diversifying into cells under the influence of stimulating factors and are able to form a series of clonal and progenitor cells.

The multipotential stain cells involved in this process are called Colony Forming Unit Scheme (CFU-S) which is based on the first study of tissue.

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