10 Examples of Innate Immunity | Their Composition and Action

Innate immunity is a part of the immune system which exists from the birth of an individual.

It is also called natural immunity as it is a basic method of defense.

This is the first line of defense against any microbial attacks on the baby.

This natural immunity is essential for the survival of the tender infant who is delicate and susceptible to many environmental microorganisms attack once out of the mother’s womb.

Innate immunity is comprised of 4 basic defense methods that mostly run throughout the entire life of the individual.

It helps in saving us from infectious attacks in almost every moment of life.

Examples of Innate Immunity

The examples consist ofInnate immunity examples

1. Physical barriers

2. Physiological barriers

3. Cellular barriers and

4. Cytokine barriers

Physical barriers

This includes skin and mucous membranes. Skin covers all the visible and environment exposed areas of the body. It is thick, hard, and keratinized making it tough for any microbes to enter the body through.

If there is a wound or cut which exposes the internal tissues, there is a chance of immediate attack of microbes on to the injury. Hence, we will notice the formation of pus and other secretion which fight with infectious bacteria and other microbes from gaining entry into the body. This lasts till the injury is covered by new skin tissue or scar during the process of healing. This pus is formed due to the rush of white blood cells to arrest the area from infection and enhance the speed of healing.

Mucous is another physical barrier and unlike skin, it is a coating on the inner surfaces of the digestive tract, intestine, respiratory system, a mouth which are frequently exposed to air, food, water from external sources. Mucous unlike skin is a temporary cover that is shed frequently and also formed frequently. It is moist and thick and enables the removal of any microbes from the body.

Epithelial cells in the inner lining of the trachea of the respiratory system have cilia. These cilia have a unidirectional movement. They entrap any dust or other particles coming in from the air outside. These trapped materials are expelled out along with phlegm.

So physical barriers like skin and mucous are examples of innate immunity.

Physiological barriers

As the name implies, these are the ones that are released or formed as a part of the body regular physiology. These include

a) Saliva is the mouth

b) Hydrochloric acid in the stomach

c) Tears in the eyes.

These three secretions prevent microbes from gaining entry into the body.

Saliva is secreted by the salivary glands in the mouth to keep it moist. This saliva has a metabolic enzyme lysozyme in it. This enzyme helps to kill the microbes present in the buccal cavity and also the food. Since the food first enters the mouth, the destruction of pathogens here limits the movement of pathogens into the body.

Hydrochloric acid is released in the stomach by the parietal cells. This hydrochloric acid keeps the pH of the gastric environment at 1.5. This highly acidic pH leads to the degradation of protein of food as well as microbes. Thus many microbes are killed in the process and prevent the chances of infection from food.

Tear in the eyes: Eyes are moist organs and also directly exposed to the environment. So, the chances of infection to the eyes are very high. But secretion of tears helps to keep these pathogens away. Tears in the eyes have many antimicrobials like the enzymes lysozyme, lactoferrin, lipocalin, secretory immunoglobulin A (IgA), enzyme secretory phospholipase A2, Secretory leukocyte protease inhibitor which kills the microbes trying to adhere to the eye surface.

Besides, there are few cationic antimicrobial peptides and surfactant protein which help in destroying the microorganisms from entering the body through the eye.

Cellular barriers

These are the immune cells in the body that kill any pathogen roaming inside the body.

These include three white blood cells viz.

a) Neutrophils

b) Monocytes and

c) Lymphocytes.Examples of Innate Immunity

Neutrophils are granulocyte type of white blood cells and are high in concentration of all the three.  They attack pathogens like bacteria, protozoa circulating in the blood, and eat them. So, they clear any pathogen from the blood circulation.

Monocytes:  These are the granulocytic white blood cells. They act as the second line of defense in the body. They convert into macrophages once they enter the tissues. These macrophages keep moving throughout body tissues. When they come across any foreign pathogen, they engulf (cell eating) them. These foreign microbes inside the macrophages are destroyed with the help of lysosomes.

Lymphocytes: These cells recognize the pathogenic microorganisms and produce antibodies against them. These antibodies bind to the pathogenic cells and their toxins and thereby neutralize them.

Thus this cellular barrier kills foreign pathogens and safeguards the body.

Cytokine barriers

These are pertinacious substances secreted by body cells to keep viruses and other pathogens at bay. When a virus infects our body cells, the infected cells produce interferons a kind of cytokines to alert the neighboring cells. There are three types of interferons like interferon-α, interferon-β, and interferon-γ. When interferons are released, they bind to the surface of other cells and signal them to produce protein to defend against viral infection and replication.

Besides, there are also other cytokines like interleukins and chemokines which also play a role in the immune system.

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