Acquired Immunity - Description and Characteristics

The immune system is your best ally when it comes to preventing illness. It has two components: innate immunity and acquired immunity. Today's article will discuss the second one, are you aware of how it works?
Acquired Immunity - Description and Characteristics
Samuel Antonio Sánchez Amador

Written and verified by the biologist Samuel Antonio Sánchez Amador.

Last update: 27 May, 2022

The immune system, both innate and acquired, is essential for optimal health. But what does acquired immunity consist of? How does it strengthen over time? Resolving these doubts is essential to enjoy a disease-free routine. Continue reading to find out more about it.

Symptoms such as ongoing colds, recurring fevers, and repeated bacterial infections can be indicative of a weakened immune system. According to the American Academy of Allergy, Asthma, and Immunology, more than three episodes of bacterial sinusitis or more than two antibiotic treatments annually, denote immune problems.

About biological barriers

The human body presents containment barriers beyond the immune system. There are three types:

  • Primary barriers. According to various studies, the skin is the first containment barrier against possible pathogens. Lipids and keratin are elements in their composition that make the epidermis a true retaining wall against viruses and bacteria.
  • Secondary barriers. Once the primary mechanisms fail, neutrophils and macrophages (white blood cells) are responsible for enveloping and destroying pathogens. We know this as phagocytosis, and it’s a clear example of a secondary barrier.
  • Tertiary barriers. T and B lymphocytes recognize many structures produced by pathogens and effectively inactivate or destroy them.

This distinction of biological barriers is essential. This is because it allows us to understand that, when we speak of the acquired immune system, we’re dealing with a tertiary biological barrier.

An illustration of cells in the immune system.
The acquired immune system is a tertiary biological barrier that allows attacking pathogens that try to infect the body.

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What’s acquired immunity?

As you can see, the acquired immunity system is defined as a set of highly specialized cells and systemic processes that eliminate or avoid pathogenic threats. This system is unique to vertebrates, according to this specialized volume on immunology.

Its function is to recognize germs in a specific way to be able to fight them quickly and more effectively. Though it may seem surprising, one can say this biological barrier has a memory, as the response to the same pathogen is increasingly powerful.

Its elements

The effectors of this protection system are T lymphocytes and B lymphocytes (blood leukocytes). These are produced in the thymus and bone marrow, respectively.

The acquired immune system can’t be understood without the innate one. As various sources point out, it’s the cells of the innate system that process the antigens (substances of viruses and bacteria) and present them to the lymphocytes. It’s all so that they act accordingly.

So as not to complicate things, we’ll limit the importance of lymphocytes to the following:

  • Each type of lymphocyte has a receptor for each antigen presented by the pathogen.
  • This information replicates in every new generation of these cells and thus generates an even more effective defense system against each wave of infection.

Symptoms of a weakened immune system

As anticipated at the beginning, there are several signs that trigger suspicion when the acquired immune system isn’t working as it should. Some of them are:

  • More than two antibiotic treatments a year
  • More than four ear infections annually
  • The development of two cases of pneumonia in close periods of time
  • Three or more episodes of chronic sinusitis annually
  • A need for preventive antibiotics to reduce the risk of infections
  • Finally, the development of serious infections from common bacterial pathologies

In meeting these requirements, a patient must undergo an immediate medical check-up. The results will be looked at by an immunologist, who’ll diagnose the underlying reason for the immunosuppression.

How to get acquired immunity

As you’ve seen, the most effective way to strengthen this tertiary barrier is none other than exposure to pathogens. This doesn’t mean you want to get sick, because vaccines already serve this purpose.

According to the World Health Organization (WHO), vaccines are preparations with weakened or dead forms of harmful microorganisms that promote the stimulation of antibodies (receptors for the aforementioned lymphocytes) when introduced into the human body.

The acquired immune system responds to these stimuli as they destroy and remember the possible threats present in vaccines. However, these don’t cause real harm to the patient. Thus, when the actual pathogen is present, the lymphocytes will recognize it immediately before the infection begins.

A doctor vaccinating a person.
Vaccination plays a very important role in strengthening an acquired immune system.

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Things to keep in mind about acquired immunity

Acquired immunity is an extremely important tertiary biological barrier. This is because it repeatedly protects humans from countless pathogens. Thus, it’s essential to be familiar with the vaccination schedules in each country and region and to follow them accordingly.

Finally, vaccines don’t only protect us by encouraging the specialization of our acquired immune system. They also generate the kind of herd immunity that protects the weakest and sickest.

Thanks for reading.

All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

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This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.