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What Is Innate Immunity?

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  • Written By: Marjorie McAtee
  • Edited By: W. Everett
  • Last Modified Date: 17 July 2014
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Innate immunity refers to those characteristics of immunity that are present at birth and passed down genetically from parents to children. It consists not only of the skin and mucus membranes, but of the blood cells responsible for fighting off pathogens like bacteria and viruses. Innate immunity is different from acquired immunity, which is not present at birth, and which occurs when the immune system fights off a pathogen and creates antibodies against that pathogen to provide future immunity.

The first major element of the innate immune system is the skin. Most pathogens cannot penetrate the skin, unless the integrity of the barrier has been compromised by injury. Ciliary action in the lungs and nasal passages helps to expel pathogens from the body before they can cause disease. Tears, saliva, urine, and the sloughing of dead skin cells are all innate immune functions that help keep pathogens from infecting the body. The mucosal lining of the digestive and respiratory tract also traps pathogens before they have a chance to take hold in the body and cause disease.

White blood cells are one of innate immunity's most important features. The different types of white blood cells include phagocytes, macrophages, and natural killer cells. White blood cells serve the immune system by identifying and eliminating pathogenic threats. These cells kill bacteria and viruses.

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The different types of white blood cells have different roles in the innate immune system. Macrophages develop when monocytes, a type of white blood cell that moves into infected tissues, enlarge and become filled with enzymes that help them eliminate bacteria. Macrophages remain in the tissues at the site of infection, removing bacteria and damaged dead cells.

Other white blood cells of the immune system have varying abilities to trap, kill, ingest, and digest pathogens. Basophils, a type of white blood cell implicated in allergic reactions, release histamine when they encounter allergens. Histamine increases blood flow to infected tissues, allowing other white blood cells more opportunity to remove invading pathogens. Dendritic cells, found in the lymph nodes and skin, help break down antigens so that T-cells can recognize and eliminate them. Natural killer cells can eliminate viruses by killing the cells that they infect.

Innate immunity comes with the built-in ability to form new immunities to specific pathogens. The white blood cells and blood proteins of the innate immune system are responsible for the body's ability to acquire immunity. Acquired immunity occurs when white blood cells create antibodies against a particular pathogen, rendering the individual immune to that pathogen's disease in the future. Acquired immunity is often induced through the use of vaccinations.

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Discuss this Article

Perdido
Post 4

@Oceana - That is so true. This can be seen in how some people’s histamine response is severe to certain irritants, while other people might not even have a histamine response.

I had an allergic reaction to some topical cream. The area where I applied it swelled up badly over the course of a day. My doctor told me that I needed to take antihistamines and apply ice to the region.

My sister used the same cream, and nothing happened to her. Our innate immunity differed, even though we are closely related.

Oceana
Post 3

I think that sneezing is a great innate immune response to invaders in the nose. The cilia do help catch things like dust that don’t belong, and then you have the uncontrollable urge to sneeze them out.

If I am in a really dusty environment, I sneeze several times in a row. This is just my body’s way of expelling the extra junk that got into my nose. If this happens and there’s any way I can, I leave the area right away.

I have always suffered from allergies, so some things that get into my nose probably make me sneeze more than other people. Certain perfumes or types of pollen have to be removed from my body promptly, while they might not even bother another person’s nose. Everyone’s innate immunity is slightly different.

shell4life
Post 2

I never really thought of my skin as helping me stay immune to diseases, but I suppose it’s true. If a section of my skin were missing, I would be much more prone to infections.

That’s probably why my mother always made me wear bandages to cover my cuts when I went to school. I was always getting into scrapes around the yard while playing, and she knew that since I didn’t have skin covering my wounds, I would need the bandage to serve as a fake skin to lock bacteria out.

Now that I’m grown, I still make it a practice to cover my cuts and scrapes. I generally do it just because it hurts to get water or dirt in them, but I’m getting the side benefit of protection from bacteria.

cloudel
Post 1

I have seen the innate immunity response at work in my own body before. I had a strange infection that caused dry, hard lumps to form in the back of my throat, and my white blood cells jumped into action against it.

My lymph nodes in my neck became swollen because of this response. I have always heard that you know you have an infection when the glands around your neck get bigger.

Because of my innate immunity, my body got rid of the infection without me ever having to go to the doctor. I felt sure that if I just waited, I would recover, and I was right.

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