Immune system

Immune system

The immune system, immune or immune system is a set of elements existing in the human body.

These elements interact with each other and aim to defend the body against diseases, viruses, bacteria, microbes and others.

The human immune system serves as a protection, a shield or a barrier that protects us from undesirable beings, antigens, that try to invade our body. Thus, it represents the defense of the human body.

Immune response

Types of body immune responses
Types of body immune responses

The body’s defense process through the immune system is called the immune response.

There are two types of immune responses: innate, natural or non-specific and acquired, adaptive or specific. Find out about each type of immune response in the explanations below.

Innate, natural or non-specific immunity

Innate or natural immunity is our first line of defense. This type of immunity is born with the person, represented by physical, chemical and biological barriers.

See in the table below what they are and how they act in defense of our organism.

BarrierAction in the organism
SkinIt is the main barrier that the body has against pathogens.
EyelashesThey help to protect the eyes, preventing the entry of small particles and in some cases even small insects.
TearIt cleans and lubricates the eyes helping to protect the eyeball from infections.
MucusIt is a fluid produced by the organism that has the function of preventing microorganisms from entering the respiratory system, for example.
PlateletsThey act in the coagulation of blood that, in the face of an injury, for example, they produce a network of threads to prevent the passage of red blood cells and retain blood.
SpittleIt has a substance that maintains the lubrication of the mouth and helps to protect against viruses that can invade the organs of the respiratory and digestive system.
Gastric juiceIt is a liquid produced by the stomach that acts in the process of digesting food. Due to its high acidity, it prevents the proliferation of microorganisms.
SweatIt has fatty acids that help the skin to prevent fungi from entering the skin.

Cream immunity is also represented by defense cells, such as leukocytes, neutrophils and macrophages, which is described below.

The main mechanisms of innate immunity are phagocytosis, release of inflammatory mediators and activation of proteins.

If innate immunity doesn’t work or isn’t enough, the acquired immunity comes into play.

Learn more about:

  • Skin
  • Platelets
  • Spittle

Acquired, adaptive or specific immunity

Adaptive immunity is the defense acquired throughout life, such as antibodies and vaccines.

It is a mechanism developed to expose people in order to evolve the body’s defenses. Adaptive immunity acts on a specific problem.

Therefore, it depends on the activation of specialized cells, the lymphocytes.

There are two types of acquired immunity:

  • Humoral immunity : depends on the recognition of antigens, through B lymphocytes.
  • Cellular immunity : defense mechanism mediated by cells, through T lymphocytes.

Read about :

  • Antigens
  • Antibodies.
  • Child vaccination

Cells and organs

The human immune system is formed by several types of cells and organs, which are divided as follows:

Types of cells and organs of the immune system
Types of cells and organs of the immune system

See below for details on how each of these cells and organs act in defense of the organism.


The defense cells of the body are leukocytes, lymphocytes and macrophages.


Leukocytes or white blood cells are cells produced by the bone marrow and lymph nodes. They have the function of producing antibodies to protect the body against pathogens.

Leukocytes are the main agent of our body’s immune system.

Leukocytes are:

  • Neutrophils : it involves diseased cells and destroys them.
  • Eosinophils : act against parasites.
  • Basophils : related to allergies.
  • Phagocytes : perform phagocytosis of pathogens.
  • Monocytes : penetrate tissues to defend them from pathogens.

Know more:

  • Leukocytes
  • Phagocytosis
  • Lymphatic system


Lymphocytes are a type of leukocyte or white blood cell, responsible for the recognition and destruction of infectious microorganisms such as bacteria and viruses.

There are B lymphocytes and T lymphocytes.

Learn more about:


Macrophages are cells derived from monocytes. Its main function is to phagocytize particles, such as cellular debris, or microorganisms.

They are responsible for initiating the immune response. See also: Macrophages


The organs of the immune system are divided into primary and secondary immune organs.

Primary immune organs

In these organs, lymphocyte production occurs:

  • Bone marrow : soft tissue that fills the inside of bones. Place of production of figured blood elements, such as red blood cells, leukocytes and platelets.
  • Thymus : gland located in the thoracic cavity, in the mediastinum. Its function is to promote the development of T lymphocytes.

Secondary immune organs

In these organs the immune response is initiated:

  • Lymph nodes: small structures formed by lymphoid tissue, which are in the path of the lymphatic vessels and are spread throughout the body. They perform lymph filtration.
  • Spleen: filters the blood, exposing it to macrophages and lymphocytes that, through phagocytosis, destroy foreign particles, invading microorganisms, erythrocytes and other dead blood cells.
  • Tonsils : made up of lymphoid tissue, rich in white blood cells.
  • Appendix : small lymphatic organ, with a high concentration of white blood cells.
  • Peyer plaques : accumulation of lymphoid tissue that is associated with the intestine.

Also learn about:

  • Lymph nodes
  • Spleen
  • Appendix

Low immune system

When the immune system does not function properly, it decreases its ability to defend our body.

Thus, we are more vulnerable to diseases, such as tonsillitis or stomatitis, candidiasis , skin infections, ear infections, herpes, flu and colds.

To strengthen the immune system and avoid problems with low immunity, special attention is needed with food. Some fruits help increase immunity, such as apples, oranges and kiwis, which are citrus fruits. The intake of omega 3 is also an ally for the immune system.

It is also important to exercise, drink water and sunbathe in moderation.

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