How does the human immune system work?

During the season of increased sickness, the need to boost immunity is talked about more often, but many people do not understand how the immune mechanisms in our bodies actually work and what it means to have good immunity.

Innate and acquired immunity

Innate(non-specific) imm unity is the same in all humans. The response occurs immediately after the microorganism enters the body and is not stored in immune memory. This means that if the same pathogen enters the body again, the system will not recognize it and will react as usual.

For more serious infections, acquired (specific) immunity plays the greatest role. The body’s response here is individual to each pathogen, and the immune memory depends on what infections the person has been through and what vaccinations he or she has received. After destroying the microorganism, the immune system remembers it and reacts much faster next time.

What cells protect our body?

The central organ of immunogenesis is the bone marrow. This is where all the cells involved in immune responses are formed. In addition, the thymus gland, where the cells mature, also plays a role in this process:

• thethymus gland, where the T lymphocytes mature;
• thespleen, where the B-lymphocytes mature. Phagocytosis is also active there, when special immune cells catch and digest microorganisms, among other things;
• lymph nodes, where immune memory cells are located, as well as immune cells that catch and absorb microorganisms.

Thus, the organs of the immune system ensure the formation, maturation, and survival of immune cells. There are many types of them in our bodies, and the main ones are:

• t lymphocytes – named after the thymus gland (Latin for Thymus) in which they mature. Specific types of T lymphocytes are responsible for different tasks, such as: killing infected cells to stop the development of infection, recognizing specific types of microorganisms, regulating the strength and duration of the immune response;
• b lymphocytes – their name comes from the Fabrician pouch (Latin: bursa Fabricii), where they were first discovered. B lymphocytes can synthesize antibodies – immunoglobulins. These are special proteins that “stick” to microorganisms and cause their death;
• nK cells – or “natural killer” cells (Natural Killer) cells. They find and kill infected and cancer cells;
• neutrophils and macrophages;
• eosinophils – protect the body from parasites;
• basophils – release large amounts of signalling substances (cytokines), which attract other immune cells to the focus of infection.

How do immune cells fight “intruders”?

They are helped by the major histocompatibility complex of the first type, MHC-i. This is a group of proteins found on the surface of cells unique to each organism. It’s a kind of cell identity card that allows the immune system to recognize what it’s dealing with. If something bad happens to a cell in the body, for example it becomes infected or cancerous, the MHC-i changes or disappears completely. Such a cell is recognized and removed.

In the case of humoral immunity, the body’s main defenders are antibodies – special proteins synthesized by B lymphocytes that bind to and neutralize foreign objects (antigens), whether a bacterium, a virus particle, or a toxin. For each type of antigen, the body is able to synthesize appropriate antibodies.

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