Allergic Diseases of the Lungs

The lungs are particularly prone to allergic re­actions because they're exposed to large quanti­ties of airborne antigens, including dusts, pollens, and chemicals. Exposure to irritating dusts or air­borne substances, often when a person is at work, increases the likelihood of allergic respiratory re­actions. However, allergic reactions in the lungs don't result only from inhaling antigens. Such a reaction may also occur from eating a certain food or taking a drug.

Text A. Types of Allergic Reactions.

The body reacts to an antigen by forming anti­bodies. The antibodies bind to the antigen, usu­ally rendering it harmless. Sometimes, however, when the antibody and antigen interact, inflam­mation and tissue damage occur. Allergic reactions are classified by the type of tissue damage that develops. Many allergic reactions are a mix­ture of more than one type of tissue damage. Some allergic reactions involve antigen-specific lym­phocytes (a type of white blood cell) rather than antibodies.

Type I (atopic or anaphylactic) reactions occur when an antigen entering the body meets mast cells or basophils—types of white blood cells that have antibodies attached to their surfaces and that are part of the immune system. When the antigen binds to these cell-surface antibodies, the mast cells release substances, such as histamine, that cause the blood vessels to dilate and the airways to narrow. These substances also at­tract other white blood cells to the area. An example of a type I reaction is allergic bronchial asthma.

Type II (cytotoxic) reactions destroy cells be­cause the antigen-antibody combination acti­vates toxic substances. An example of a disease caused by a type II reaction is Goodpasture's syn­drome.

Type III (immune complex) reactions occur when large numbers of antigen-antibody complexes ac­cumulate. They may cause widespread inflam­mation that damages tissues, particularly blood vessel walls, a condition called vasculitis. Sys­temic lupus erythematosus is an example of a disease that results from a type III reaction.

Type IV (delayed or cell-mediated) reactions occur when an antigen interacts with antigen-specific lymphocytes that release inflammatory and toxic substances, attract other white blood cells, and injure normal tissue. The skin test for tuberculo­sis (tuberculin test) is an example of this type of reaction.

Notes:

prone склонный, подверженный

render возмещать, компенсировать

bind связывать

mediated опосредованный

dilate расширять

 

Text B. Eosinophilic Pneumonia.

Eosinophilic pneumonia, also called pulmonary in­filtrates with eosinophilia (PIE) syndrome, consti­tutes a group of lung diseases in which eosinophils, a specialized type of white blood cell, appear in increased numbers in the lungs and usually in the bloodstream.

Eosinophils participate in the immune defense of the lung. The number of eosinophils increases during many inflammatory and allergic reactions, including asthma, which frequently accompanies certain types of eosinophilic pneumonia. In eosinophilic pneumonias, the tiny air sacs of the lungs (alveoli) and often the airways fill with eosino­phils. Blood vessel walls may also be invaded by eosinophils, and the narrowed airways may be­come plugged with mucus if asthma develops.

The exact reason that eosinophils build up in the lungs isn't well understood, and often it isn't possible to identify the substance that's causing the allergic reaction. But some known causes of eosinophilic pneumonia include certain drugs, chemical fumes, and fungal and parasitic infec­tions and infestations.

Symptoms and Diagnosis

Symptoms may be mild or life threatening. Sim­ple eosinophilic pneumonia (Loffler's syndrome) and similar pneumonias may produce mild fever and mild respiratory symptoms, if any. A person may cough, wheeze, and feel short of breath but usually recovers quickly. Occasionally, an eosin­ophilic pneumonia can progress to severe respi­ratory failure in a few hours.

Chronic eosinophilic pneumonia is severe, and if untreated, often it gets worse. Life-threatening shortness of breath can develop.

With the eosinophilic pneumonias, tests show large numbers of eosinophils in the blood, some­times as many as 10 to 15 times the normal num­ber. A chest x-ray usually shows shadows in the lungs that are characteristic of pneumonia. How­ever, unlike pneumonia caused by bacteria or vi­ruses, eosinophilic pneumonias typically show rapidly appearing and disappearing shadows on serial x-rays. Microscopic examination of coughed-up sputum typically shows clumps of eosinophils rather than the sheets of granulocytes that are found in bacterial pneumonia. Other laboratory tests may be performed to search for a cause, especially an infection with fungi or parasites; these tests may include micro­scopic examination of stool specimens. A doctor also considers whether any medication the pa­tient is taking may be the cause.

Treatment

Eosinophilic pneumonia may be mild and may get better without treatment. For severe cases, a corticosteroid such as prednisone is usually needed. If a person also has asthma, routine asthma treatment is given as well. If worms or other parasites are the cause, they're treated with appropriate drugs. Ordinarily, drugs that may be causing the illness are discontinued.

Notes:

constitute составлять

shortness недостаток, нехватка

infestation инвазия

clup комок, глыбка, слепок (о мокроте)

routine плановый, обыденный, рутинный