Immune response: everything you need to know

The immune response is a process based on the human immune system that allows the body to identify external agents and attack them. It is a complex mechanism that we explain here.

The immune response is an essential mechanism of the body to defend ourselves from external agents that can be harmful to our health. It is made up of different processes and cells that carry them out. Here we tell you everything you need to know about it.

What is the immune response?

The immune response is the set of phenomena that the body carries out to recognize and eliminate external agents that it perceives as harmful. These phenomena are based on the recognition of these foreign substances, which are called antigens.

Antigens are usually parts that are found on the surface of viruses, bacteria, and fungi. Likewise, other inert substances, such as some chemicals, chips of different materials, or toxins, can also be recognized as antigens.

People have two different types of immunity. Next, we are going to tell you what each one of them consists of.

Innate immunity

Innate immunity is not specific. It is present even before having contact with the specific antigen. All people have this type of immunity from the moment of birth. We can divide this type of immune response into two different mechanisms:

  • Barriers: barriers can be physical, such as the skin, that prevent the substance from passing through the body, or chemical. There are many chemical barriers present in our body. These would be, for example, nasal mucus, tears, saliva or vaginal discharge. These substances have characteristics that make it difficult for a virus or bacteria to survive. As an example, we can mention the pH of the vaginal discharge, in which most pathogens cannot live.
  • Cell mechanism: composed of the complement system, the inflammation mechanism and phagocytes. The three mechanisms are based on substances that are present in our blood, continuously circulating through the blood vessels. When a foreign agent manages to reach the interior of the body, these systems are activated to eliminate it.

Specific immunity

This is the second type of immune response. Unlike the innate response, we are not born with developed specific immunity. This is being formed as the body comes into contact with different antigens. It is faster and more efficient acting in the elimination of pathogens.

The tissue responsible for this type of immunity is lymphoid tissue, made up of organs such as the spleen or thymus, and lymphatic vessels. Lymphocytes are produced in this tissue, which will be the cells in charge of carrying out this type of immune response.

Thus, antigens are recognized by specific parts of them called epitopes. When an antigen enters the body, innate immunity is activated, which is faster to activate, but less effective, and the specific one is slower, but is much more effective.

A lymphocyte will recognize the epitope of the antigen. Lymphocytes are responsible for producing substances called antibodies, which will be responsible for eliminating the pathogen. In addition, this lymphocyte will activate more lymphocytes that will come to the site to help eliminate the antigen. This is the primary specific immune response.

Aside from the primary immune response, memory lymphocytes are also produced. These memory lymphocytes will cause specific immunity to be activated more quickly, in case of re-contact with the same type of antigen, eliminating the harmful agent. This will be what we know as the secondary immune response.

What are passive immunity and active immunity?

Active immunity is about the entire complex that we have previously reported. It is the one carried out by the human body naturally when it comes into contact with an antigen. First the innate immune response will be activated, then the primary specific one, and finally, and in case of successive contacts, the secondary immune response.

On the other hand, in passive immunity, specific antibodies are already circulating in the body without having been in contact with the antigens. This can happen twice:

  • Newborn babies: by antibodies that the mother passes to the fetus during pregnancy.
  • Vaccinated: the vaccines may consist of antibodies or fragments of the pathogen that consistently produce memory cells without causing the disease.

The immune response is a defense system

Immunity is a natural defense system of the body. Although it is present in all of us, there are different ways in which we can take care of and keep our immune systems in good condition. We must try to be up to date with vaccines, and try to make our immune system healthy.

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