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The body's immune system

The human body is exposed to harmful factors every day. To survive in this environment, it uses mechanisms that fight infections.

The basic task of the immune system is to distinguish between the enemy and its own cells. The cells have special, unique proteins on the surface - antigens that act as identification cards. Thanks to them, the immune system is able to identify bacteria, fungi, viruses, toxins and contaminants as foreign and tries to destroy them.

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Schemat przedstawiający obszary działania sytemu odpornościowego. Na środku umieszczone jest zielone koło z siedmioma strzałkami z napisem: układ immunologiczny. Wokół koła zielonego są koła niebieskie z napisami: bakteria; wirusy; grzyby; pasożyty; obce białka; toksyny wytwarzane przez bakterie, grzyby, rośliny i zwierzęta; zanieczyszczenie chemiczne.

Non‑specific immunity

The body has 2 defence systems – non‑specific and specific. Non‑specific immunitynon‑specific immunityNon‑specific immunity can be acquired or congenital. Mechanisms of innate non‑specific immunity protect the body from the invasion of pathogens. This non‑specific immunity is based on physical, chemical and cellular barriers.

Physical barriers act as mechanical protection and are the first obstacle that pathogenspathogenpathogens encounter on their path. To prevent from the penetration of pathogens, the body is protected by the skin and the mucous membranes of the gastrointestinal, respiratory and urinary tracts. Defensive reactions such as sneezing, coughing and vomiting help to remove intruders from the body.

The chemical barriers are secretions: sweat, tallow, hydrochloric acid in the stomach and tears and saliva which contain substances that destroy bacteria and viruses. The cell barrier is made up of defensive cells including leucocytes and macrophages. They become active when pathogens overcome the physical and chemical barriers and penetrate into tissues. Leucocytes secrete substances that raise the body's temperature above normal. In this way, the body creates adverse conditions for the development of bacteria. Unfortunately, a very high fever is also deadly for the body itself.

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Grafika przedstawiająca bariery układu odpornościowego w ludzkim ciele. Na sylwetce człowieka oznaczono następujące elementy: 1 łój tallow is a barrier preventing the penetration of microorganisms and limits the growth of bacteria and fungi, 2 łzy tears and enzymes tight in them cleanse the eyeball all the time, 3 woskowina uszna substances secreted in the ear limit the growth of bacteria, 4 nabłonek rzęskowaty płuc the ciliated epithelium of the airways removes contaminants and photogenic microorganisms, 5 pot low sweat pH limits the development of pathogenic organisms, 6 was żołądkowy hydrochloric acid in the stomach eliminates most of the microorganisms taken with food, 7 skóra skin is a physical barrier, 8 kwaśne pH acid pH in female reproductive tracts and antibacterial proteins in semen limit bacterial growth, 9 uszczelnienie rany wound sealing closes the pathways of microorganisms penetration

Sometimes when we get hurt, bacteria can penetrate the wound which provides favourable conditions for multiplication. Macrophages travel to these wounds and move to fight bacteria. They devour them and then they themselves breakdown, releasing proteolytic enzymes. Inflammation occurs. The area around the wound becomes red, swollen and painful. Under the influence of enzymes, damaged and dead cells are digested and the wound is filled with pus.

Specific immunity

When the mechanisms of non‑specific immunity fail, pathogens enter and spread within the body's tissues. The immune system responsible for the creation of the specific immunityspecific immunityspecific immunity then becomes involved. It consists of recognising and disposing of specific microorganisms. There is mobilisation of white blood cells - macrophages and T- and B- lymphocyteslymphocyteslymphocytes.

Germs have specific proteins called antigens on the surface. B‑lymphocytes present in the blood produce antibodies specific to these antigens that match them like a key to a lock. At the time of contact with the foreign antigen, the number of antibodies in the body increases. After identifying the enemy, the antibodies surround it and signal for macrophages to destroy the indicated objects. After the eradication of the foreign object in the blood, a group of lymphocytes remain - memory cells, which in the event of another infection are able to quickly multiply and produce appropriate antibodies to fight the germs, preventing the development of infection.

T‑lymphocytes support immune system reactions. They are divided into several groups. Some excrete specific substances that destroy own cells, infected with microorganisms and those with cancerous changes. They are also responsible for the discards of transplanted tissues. The second group facilitates the activation of B lymphocytes and macrophages and secretes specific proteins that activate the body's defense mechanisms (eg anti‑drug production) and enable communication between cells of the immune system. The next group quenches the inflammatory reaction. The part of T lymphocytes has immunological memory, thanks to which we fight the next infection faster.

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Grafika przedstawia reakcje obronne organizmu.Ilustracja przedstawia z lewej główkę kości udowej w przekroju. Wewnątrz ma czerwonawe ziarnistości, podpisane jako marrow. Od niego dwie strzałki, symbolizujące limfocyty powstające w szpiku kostnym. Górna do zielonej trójkątnej grasicy podpisana thymus, dolna do różowej rurki – naczynia krwionośnego w przekroju podpisane blood vessels. Niebieska kulka z wypustkami to limfocyt B, podpisana B lymphocyte, a z grasicy strzałka wskazuje żółtą kulkę, czyli limfocyt T, podpisany T lymphocyte. Rysunek poniżej przedstawia przekrój przez różowo- zielony węzeł chłonny z naczyniami krwionośnymi. Podpis: lymphocytes and blood reach the lymph nodes; lymph node

Active and passive immunity

Active immunityActive immunityActive immunity involves the production of antibodies and memory cells, either in a natural way as a result of an infection (natural active immunitynatural active immunitynatural active immunity), or after administration of a vaccinevaccinevaccine (artificial active immunity). Vaccines contain weakened or killed pathogenic microorganisms. They mobilise the immune system but are too weak to cause disease. Vaccines are given in advance, before a person comes into contact with the germs. When a vaccine is given, the organism has ready‑made defense tools at the onset of a given pathogen, and prevents the disease from developing or combats it very quickly.

Some vaccinations are mandatory, others are recommended. The first ones are free of charge and run according to the vaccination schedule from the birth of a child up to age of 19. On the first day after birth, the child receives a vaccination against tuberculosis and hepatitis B. In subsequent years, they receive further vaccinations. The teenager should have the vaccine against diphtheria, tetanus and pertussis at the age of 14. This vaccination is repeated at the age of 19. Other vaccinations are recommended which provide for a wider protection against infectious agents. These include among others: influenza, tick‑borne encephalitis and human papillomavirus (HPV).

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Wykres przedstawia w postaci linii dane na temat zachorowań na odrę. Na osi X lata od 1975 do 2010. Na osi Y z lewej zachorowania od zera do 160 tysięcy, podpisano disease, z lewej odsetek zaszczepionych od zera do 100 procent, podpisany: percentage of vacclnared people. Kolor pomarańczowy oznacza zachorowania osób nie szczepionych ( disease). Linia zielona oznacza zachorowania ludzi zaszczepionych w dziesiątym roku życia ( vacinated at the age of 10). Linia niebieska oznacza osoby, zaszczepione w trzecim roku życia ( vaccinated at the age of 3). Ze wzrostem odsetka osób zaszczepionych maleje liczba zachorowań.

Passive immunityPassive immunityPassive immunity can be obtained thanks to ready‑made antibodies delivered to the body from the outside. For example, after being infected with a particularly dangerous disease serumserumserum is administered. It comes from the blood of animals that have gone through the disease and contains antibodies. They are ready to fight antigens immediately in the infected organism. In this way, you get the artificial passive immunityartificial passive immunityartificial passive immunity. Newborns have natural passive immunitynatural passive immunitynatural passive immunity - in their early lives, antibodies produced by the mother's immune system are transmitted by the placenta and then together with milk during breastfeeding.

Transplantation

The immune system can recognise, remember and distinguish between its own cells and others. Unfortunately, in some situations this skill of the immune system can be harmful rather than helpful. This applies to those sick people or victims of accidents, for whom the only way to save their health or life is transplantationtransplantationtransplantation (graft). Acceptance of the graft depends on the compatibility of antigens on the surface of the recipient and donor cells. The greater the compatibility, the greater the chance of acceptance of transplant. 100% acceptance is achieved through auto‑graft (e,g. the transfer of a healthy skin fragment to a damaged part of the body of the same person). Transplants between identical twins who have the same antigens in general end successfully. The more distant the relationship between the donor and the recipient, the greater the likelihood of rejection of the transplant.

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Ilustracja przedstawia fragment sylwetkę człowieka z lokalizacją najczęściej przeszczepianych narządów. Są to: 1 płuca- lungs, 2 wątroba- liver, 3 kość uda- marrow, 4 skóra- skin, 5 serce- heart, 6 trzustka- pancreas, 7 nerka- kidneys

Most organ transplants come from deceased people. According to Polish law, when doctors have confirmed death, the person is a potential organ donor, provided that they have not previously expressed a written objection in the Central Register of Objections in the Organisation and Coordination Centre for Transplantation or as a verbal statement in the presence of witnesses. In practice, doctors discuss it with deceased's family. When the family does not agree to organ donation, their wish is respected and the deceased is withdrawn from organ donation. This is a reason why many patients can not be saved or be helped in making a recovery. Each of us are able to help our family and doctors with the decision by carrying a completed declaration of will.

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Ilustracja przedstawia formularz. W nagłówku napis: Declaration of will. Dalej tekst: In the hope of saving the lives of others, I agree to take my tissues and organs for transplantation after death. Niżej miejsca do wpisania danych osobowych: Name, Surname, Date of birth, Social Security, Addres, Date, Signature

Summary

• Non‑specific immunity is the first line of defense, protects the body against the penetration of pathogenic agents.

• Specific immunity is involved in: macrophages, T lymphocytes, B lymphocytes and antibodies. Macrophages consume a pathogenic agent.

• T lymphocytes destroy the cell‑infested cell.

• B lymphocytes produce antibodies that neutralize the pathogen.

• Antibodies fight only 1 type of antigen.

• Specific immunity is produced by contact with the antigen (active immunity) or by the administration of ready‑made antibodies (passive immunity).

• As a result of the first contact with the antigen, T and B lymphocytes are formed that remember the image of the antigen and constitute memory cells that quickly fight against the given antigen when they come back into contact with it.

• Transplants involve the transplantation of cells, tissues and organs from the donor organism into the recipient organism in order to save his health or life.

Keywords

immune system, T lymphocytes, B lymphocytes, macrophages, antigen, antibody

Glossary