Phagocytosis and the production of antibodies by leukocytes is a single defense mechanism called immunity.
Immunity – protection of the body from foreign substances and organisms.
The mechanisms of immunity protect the body from infectious agents (bacteria and viruses), free it from dead and degenerated cells.
Immunity reactions are the reason for the rejection of transplanted organs and tissues.
Complications from transfusion of an incompatible blood type are also associated with immune responses.
The thymus, or thymus gland, plays a very important role in the formation of immunity. This gland is located behind the breastbone and functions well only in children.
Types of immunity
From birth, people are immune to many diseases, as their blood contains ready-made antibodies. Such immunity is called congenital. Congenital immunity is inherited from the parents.
from birth, a person has immunity to the causative agent of dog plague. The human body is protected from this disease.
If a person has suffered an infectious disease, then antibodies are also formed in his body – immunity is formed. Such immunity is called acquired. If the same pathogen after a while again appears in the body, it is immediately destroyed. Therefore, people who have had measles or chickenpox in childhood usually do not get sick with them again.
having had measles, whooping cough, chickenpox, people, as a rule, do not fall ill with these diseases again.
Congenital and acquired immunity is called natural.
To protect a person from contracting a particular infectious disease (smallpox, rubella, mumps (mumps), poliomyelitis, diphtheria, etc.), a person is vaccinated – a vaccine is injected (killed or severely weakened pathogens) and thus create artificial immunity.
Vaccination causes mild disease, and protective antibodies are formed. This is active immunity. Vaccinations have saved many lives.
In 1769, the English physician Edward Jenner noticed that peasant women caring for cows quite often contract the disease “cowpox” from animals, which is easy in humans. And during periods of epidemics, those who had been ill with “cowpox” never had human smallpox (a very dangerous, often fatal human disease). Jenner first inoculated an eight-year-old boy with “cowpox”, and after 1.5 months he infected him with human smallpox. The child did not get sick. Thus, vaccinations were developed.
If a sick person needs help quickly, he is usually injected with ready-made antibodies in the form of a therapeutic serum, which is obtained from the blood plasma of animals or people who have had an infectious disease. This is passive immunity.
medicated sera are often the only treatment for life-threatening diseases such as tetanus. The causative agent of tetanus is in the soil and, if the wound is contaminated with soil, it can enter the body and cause this serious illness. If tetanus is suspected, tetanus toxoid should be administered urgently in a hospital.
However, antibodies introduced into the body with serum are short-lived, and after a while a person becomes susceptible to this disease again.
Medicinal serum is a blood plasma preparation without fibrinogen, containing ready-made antibodies that have formed in the blood of an animal (or a person) previously infected with this pathogen (who has suffered this disease).
Types of immunity
There are two types of immunity: specific and non-specific.
Nonspecific immunity is species-specific, that is, it is practically the same in all representatives of the same species. It is directed against any foreign substances and ensures the fight against infection in the early stages of its development, when specific immunity has not yet been formed.
Nonspecific immunity is innate. It is formed already in the fetus and is provided by the skin and cells of the mucous membranes.
The state of nonspecific immunity determines a person’s predisposition to various commonplace infections, the causative agents of which are conditionally pathogenic microbes.
Specific immunity is individual in nature and is formed throughout a person’s life as a result of contact of his immune system with various microbes and antigens. Specific immunity is provided by antibodies secreted by lymphocytes, and is directed to a specific antigen.
The specific immunity preserves the memory of the previous infection and prevents its recurrence.