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What Is Adaptive Immunity?

Past exposure to antigens helps create adaptive immunity.
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  • Written By: Tricia Ellis-Christensen
  • Edited By: O. Wallace
  • Last Modified Date: 26 September 2014
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Adaptive immunity is an important part of the immune system that governs how the body responds to infectious agents or antigens to which it has been previously exposed. Past exposure to an antigen in either its natural or created forms may create a memory of the antigen’s presence. Future exposure, once adaptive immunity or specific immunity is acquired, results in a quick and effective response. The body mobilizes B and T cells to fight subsequent exposures before they create illness and the person remains well. This brief description presupposes that specific, adaptive or acquired immunity is functioning normally, which isn’t always the case.

There are two main elements of the immune system, which are broken down into innate and adaptive immunity. Innate immunity is the body’s natural response to any exposure to an antigen. The healthy person’s innate immune system works in a variety of ways to fight any disease exposure and end illness, though it isn’t always successful. In contrast, adaptive immunity is developed through antigen exposure or interventions like vaccination. It’s usually faster and more effective, but it is also antigen-specific. It only works when the body has memory of fighting a specific germ before.

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Adaptive immunity depends on the body recognizing an antigen to which it has been previously exposed. When that recognition occurs, the body shifts into a high-geared response that can defeat the antigen’s ability to take hold and result in sickness. This response isn’t always perfect, and some people develop partial immunity to illnesses and aren’t able to fully fight them. Also, adaptive immunity to some things can wear off over time, or certain types of viruses and bacteria don’t cause adaptation through exposure.

People with autoimmune diseases may have inappropriate adaptive immunity responses. The body may view any substance, even part of itself, as foreign, and mobilize B and T cells to attack itself. Over time, severe damage can occur, and these illnesses need to be treated with medications that dull both types of immune response.

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SteamLouis
Post 3

Adaptive immunity is one of the miracles of the human body in my opinion. When the body fights an antigen for the first time, the genetic makeup of cells literally change. So when a white blood cell comes across that antigen again, it recognizes it and attacks! It's just amazing.

If it wasn't for this system, humans couldn't have survived the types of epidemics that have occurred throughout history. Humanity would have probably ended.

ysmina
Post 2

@fBoyle-- I'm not an expert on this topic but I think that has to do with the number and variety of antigens.

There are many different strains of the flu virus and they change all the time. Since it's impossible for an individual to become immune to every single strain out there, an annual vaccination is necessary for protection. Immune cells can only react to an antigen early if they have memory of fighting that antigen before. If they don't have memory about the antigen, they can't fight it.

I guess the chicken pox virus does not mutate or doesn't have many strains, so the immune cells have memory of it and fight it quickly.

fBoyle
Post 1

Why does the body develop different types of adaptive immunity to different illnesses?

I mean, when someone gets chicken pox as a child, he or she will probably not get it again. But someone can get the flu again and again despite getting vaccinated for it every year. Why?

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