Immunity: What It Is and How the Immune System Works

You have had a cold for the third week in a row, and acquaintances are already saying: "your immunity has dropped." Let's figure out what lies behind this. Immunity is the body's ability to recognize and remove foreign material: bacteria, viruses, altered own cells.

What immunity is

Immunity is the ability to maintain one's biological individuality. The body recognizes and removes foreign substances and cells. This includes pathogenic bacteria, viruses, and the body's own modified tumor cells.

The immune system distinguishes "self" from "non-self," remembers the first contact with an antigen, and works through clones of cells. One clone usually responds to one antigenic determinant.

What the immune system consists of

There are central and peripheral organs. The central ones are the red bone marrow and the thymus. B lymphocytes mature in the bone marrow, and T lymphocytes mature in the thymus.

The peripheral organs are the spleen, lymph nodes, and mucosal immune system. It is represented by lymphoid tissue in the bronchi, intestines, and nasal cavity. The spleen is the largest organ of the immune system: the white pulp occupies 20%, the red pulp 80%.

The red pulp of the spleen stores mature formed elements of the blood, monitors the condition and destruction of old red blood cells and platelets, and participates in phagocytosis of foreign particles. Macrophages and lymphocytes participate in the immune response. Lymphocytes are divided into subpopulations: T helpers, cytotoxic T lymphocytes, NKT.

Innate and acquired immunity

Innate immunity works before the first encounter with a pathogen. It recognizes common features of different microbes, has no strict specificity, and does not remember contact. Most of its cells belong to the myeloid lineage.

Acquired, or adaptive, immunity responds to specific antigens. It has a clonal response, lymphoid cells, and immunological memory. Autoaggression is also possible.

Active, passive, natural, and artificial immunity

Acquired active immunity arises after an illness or after administration of a vaccine. Acquired passive immunity develops with the administration of ready-made antibodies with serum or when they are passed to a newborn with the mother's colostrum.

Natural immunity includes innate immunity, acquired active immunity after illness, and passive immunity when antibodies are passed to the child from the mother. Artificial immunity includes active immunity after vaccination and passive immunity after administration of serum.

Disorders of the immune system

Disorders of the immune system include autoimmune diseases, allergy, primary immunodeficiencies, and HIV.

• autoimmune diseases;
• allergy;
• primary immunodeficiencies, for example severe combined immunodeficiency;
• HIV.

Vaccines and infectious diseases are also connected with the immune system.

Reduced immunity in itself is not a reason to call an ambulance. 103 or 112 — for a life-threatening condition, for example signs of stroke or heart attack.

The material is for reference and does not replace consultation with a doctor.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer