Immunity

There are four ways to acquire specific immunity: active natural, active artificial, passive natural, and passive artificial. Natural and artificial refer to the method of exposure. Natural exposure implies that contact with antigen or antibody (protein found in the plasma is responsible for humoral immunity) occurrs as part of everyday living and was not deliberate. Artificial exposure, also called immunization, is a deliberate introduction of antigen or antibody into the body.

"Active" and "passive" describe whose immune system is responding to the antigen (antigens are large molecules that stimulate a specific immune system response). When the individual is exposed to the antigen (either naturally or artificially), there can be a specific immune system response, which is called active immunity because the individual's own immune system is the cause of the immunity. Passive immunity occurs when another person or animal develops immunity and the immunity is transferred to a nonimmune individual.

Active natural immunity results from natural exposure to an antigen. Because the individual is not immune during the first exposure, he/she usually develops the symptoms of the disease. Interestingly, exposure to an antigen does not always produce symptoms. In active artificial immunity an antigen is deliberately introduced into an individual to stimulate his/her immune system. This process is vaccination, and the introduced antigen is vaccine. Injection of the vaccine is the usual mode of administration (tetanus toxoid, diphtheria, and whooping cough), although ingestion (Sabin poliomyelitis vaccine) is sometimes used. Passive natural immunity results from transfer of antibodies from a mother to her fetus or baby. Achieving passive artificial immunity usually begins with vaccinating an animal such as a horse. After the animal's immune system responds to the antigen, antibodies are removed from the animal and are injected into the individual requiring immunity.

Ex. 21. Translate the following abstract without using dictionary:

Immunity can be natural or artificial, innate or acquired, and active or passive.

Active natural (contact with infection): develops slowly, is long term, and antigen specific.

Active artificial (immunization): develops slowly, lasts for several years, and is specific to the antigen for which the immunization was given.

Passive natural (transplacental = mother to child): develops immediately, is temporary, and affects all antigens to which the mother has immunity.

Passive artificial (injection of gamma globulin): develops immediately, is temporary, and affects all antigens to which the donor has immunity.

Ex. 22. Read the following text, entitle it, and discuss obtained information with your fellow-student:

Disorders in the immune system can cause various diseases. Immunodeficiency diseases occur when the immune system is less active than normal, resulting in recurring and life-threatening infections. Immunodeficiency can either be the result of a genetic disease, such as severe combined immunodeficiency, or be produced by pharmaceuticals or an infection, such as the acquired immune deficiency syndrome (AIDS) that is caused by the retrovirus HIV. In contrast, autoimmune diseases result from a hyperactive immune system attacking normal tissues as if they were foreign organisms. Common autoimmune diseases include rheumatoid arthritis, diabetes mellitus I, and lupus erythematosus. These critical roles of immunology in human health and disease are areas of intense scientific study.

Both immune cells and foreign molecules enter the lymph nodes via blood vessels or lymphatic vessels. All immune cells exit the lymphatic system and eventually return to the bloodstream. Once in the bloodstream, lymphocytes are transported to tissues throughout the body, where they act as sentries on the lookout for foreign antigens.

We are all born with a genetically based natural defense system. The skin is the most important organ of our natural defense system. An injury is a gateway for germs to enter the body. This, or the presence of a foreign object within the body, causes the immune system to act, getting rid of the invaders, while the skin takes care of the wound. When this process does not take place, it results in an infection. Another sign of the functioning of the immune system is when we get a rash or a bump on the skin after a mosquito bites.

When you have a vaccination, your immune system is given a copy of a specific disease, so that if the system comes across the disease again, the memory cells in the immune system will know exactly what action to take, likewise, if you have had a disease before, they know what to do in the event of reinvasion.

Ex. 23. Make up a dialogue on the immune system.

Ex. 24. Translate the following sentences into English:

1. Лімфатичні вузли, селезінка, червоний кістковий мозок і загруднинна залоза об’єднуються в імунну систему. 2. Імунна система забезпечує захист організму від генетично чужорідних клітин та речовин. 3. Імунітет – це спосіб захисту організму від інфекційних і неінфекційних агентів та речовин, які мають ознаки чужорідної генетичної інформації. 4. Залежно від механізмів, які формують несприйнятливість організму до патогенних факторів, виділяють такі основні види імунітету: природний та штучний, активний та пасивний. 5. Імунна система включає всі органи, в яких відбувається утворення і диференціація клітин, що здійснюють захисні реакції організму. 6. Найважливіші клітини імунної системи – це лімфоцити, які поділяються на Т-лімфоцити і В-лімфоцити.