Immune system - types of threats and mechanisms of action (part 1)

The immune system is one of the most important systems of the human body and at the same time one of the most complex . It consists of organs, vessels and immune cells, but the number of mechanisms and ways of counteracting threats is really large and complicated. Its task is to protect the body from threats, such as cancer cells and pathogens (foreign bodies that are disease-causing factors).

Types of threats and natural barriers

The most basic division of threats and barriers that counteract them is into mechanical, chemical and biological. These are the basic mechanisms, the simplest in operation. They constitute the first barrier that acts non-specifically (i.e. they always act the same, regardless of the type of threat). They include:

• reflexes (sneezing, coughing, tearing – this allows the body to remove threats)
• mucus (found in many internal parts of the body, makes it difficult for harmful microorganisms to grow)
• enzymes (substances that are constantly acting in the body at different angles, some have antibacterial properties, are found e.g. in saliva)
• bacterial flora (the human body has "good bacteria" from birth, they perform a number of useful functions, including immune functions)
• acidic pH (the pH of individual places in the body is different, for example blood is in the neutral range [pH 7.35-7.45], but in many places, such as the stomach it is much lower, which kills most bacteria and viruses)

All of these elements are a physiological basis, meaning that in a healthy organism they are constantly regulated and provide a certain degree of immunity. They require support only in certain pathological (i.e. abnormal) conditions.

Basic immune organs

We divide them into two groups:

• Central – some immune cells are produced in them and then respond when needed. This group includes the bone marrow and the thymus.
• Peripheral – this is where the body's immune response takes place, i.e. counteracting pathogens. Peripheral organs are lymph nodes, spleen, lymph nodes, appendix (once downplayed), Waldeyer's pharyngeal ring

All of these organs are responsible for ensuring the proper production and functioning of immune cells.

Specific and nonspecific immunity

These are two types of immunity, to which all mechanisms are attached. Non-specific immunity is innate mechanisms and more general actions, not directed against specific threats; they always work in the same way, regardless of what the body is attacked by. The opposite is specific immunity ; it is the acquired ability to eliminate individual threats. It works in a specific way, i.e. adapted to a specific threat, and the way of reaction is different depending on what the body attacks.

Basic immune cells

This is a rather complicated topic, so it is worth focusing on the basics. Immune cells are leukocytes (white blood cells) determined in a popular blood count test. They are divided into granulocytes (neutrophils, eosinophils and basophils) and agranulocytes (lymphocytes and monocytes), which is also taken into account in basic tests, along with their proportions. The first group is produced in the bone marrow, is responsible for, among other things, allergic reactions, counteracting parasites. An increase in these cells is also noted, for example, in chronic inflammation or leukemia.

The second group are monocytes and lymphocytes:

The former perform their functions in the form of antigen-presenting cells (in simple terms, they enable the recognition and stimulation of other cells that will direct their actions against a specific threat) and macrophages (these are phagocytic cells that are the first to reach the site of threat in the body; they secrete bactericidal substances and carry out the process of phagocytosis – they absorb the element of the threat and digest it).

Lymphocytes, on the other hand, are responsible for specific immunity, and can be called a “specialized” group. A simple example is the administration of vaccines: a weakened pathogen is administered to the human body, which does not pose a threat, but the body recognizes it and produces immunity against it; when the pathogen re-enters the body after some time, the immune mechanism is ready to react. They act against a specific, recognized threat and are directed only against it. They are divided into two main groups: B lymphocytes (producing antibodies) and T lymphocytes, and then into subsequent, smaller groups.

In addition to lymphocytes, it is worth mentioning NK cells (Natural Killer). They have some connections with lymphocytes and their function is to kill the appropriate cells.

Free oxygen radicals – enemy and ally

As you can read earlier, some of the immune cells - macrophages, produce phagocytic substances that kill pathogens. There are many of these substances, but it is worth saying a few words about the most popular free radicals. The concept appears in the mass media, most often in advertisements for products that reduce the number of free radicals, so it is worth knowing what we are really dealing with. In simple terms, without delving into chemistry: these are oxygen molecules that have an unpaired electron, which makes them toxic to organisms. The immune system uses them to fight threats, but too much of them can be harmful to us.

Inflammation

By definition, it is a process that develops under the influence of a damaging factor, the purpose of which is to protect the organism. Such a factor can be, for example, a microorganism, physical or chemical damage. Inflammation aims to remove the factor that poses a threat and allow the organism to return to normal functioning. Accompanying symptoms include fever, pain, swelling, and sometimes loss of organ function. The problem, however, is when inflammation becomes chronic - then it must be combated, because it is a factor that increases mortality.

Microbiota

This term covers all microorganisms living in the human body. In the context of immunity, we focus on "beneficial bacteria" - they occur in the oral cavity, nasal cavity, intestines, lungs, vagina, on the skin. Microflora is largely responsible for immunity, which is why it is worth taking care of it, by supporting it with proper nutrition or avoiding steroids and antibiotics. The flagship microorganisms are from the Lactobacillus group. They acidify the environment in which they are found, which makes it difficult for pathogenic bacteria to grow, and they also produce antibacterial substances and compete with "bad bacteria" for food.

The human body has many mechanisms responsible for its defense. The immune system is one of the most complex: it has the ability to react both generally, more prophylactically, and specialized, acting in specific cases. Its proper functioning is important, it allows the body to protect itself from diseases.