An Inflammatory Situation

PART 1 Asthma: Constant Inflammation of the Airways

Asthma, also called bronchial asthma, can have different triggers and may create anything from mild to severe symptoms. But there is one thing all cases of asthma have in common: chronic (long-term) inflammation. When you have asthma, your airways—specifically, your bronchioles—are always inflamed. READ MORE

Normally, inflammation is your immune system’s helpful response to injury and leads to the repair of the injured tissue and a return to normal function. But in asthma, the inflammation doesn’t end. It becomes self-perpetuating: the immune cells in the tissues of your airways recruit more and more immune cells to the site. They become a permanent presence in your lungs.

With this prolonged inflammation, your lungs become hyperreactive—that is, supersensitive to irritants or allergens. They react excessively to triggers such as tobacco smoke, pollen, pet dander, exercise, viruses, or cold air.

The degree of sensitivity varies from individual to individual. Some people with asthma are hypersensitive to environmental triggers, while others are only mildly sensitive and may have no symptoms at all. LESS

PART 2 When Your Lungs Overreact

Whether or not you have asthma, the bands of smooth muscle tissue surrounding your bronchioles constrict (narrow) slightly in the presence of allergens or irritants. In people who don’t have asthma, this constriction is followed by relaxation of the smooth muscle so that the airways open and the irritant can expelled. READ MORE

However, in people with asthma, the smooth muscle remains constricted. Why exactly this happens is not clearly understood. The continued narrowing of the airways makes both inhaling and exhaling more difficult. LESS

PART 3 The Inflammatory Cascade

Inflammation is a normal and necessary process of your body’s immune system. When you are injured or a foreign body invades your system, leukocytes (white blood cells) in your bloodstream swarm to the affected region. There are many different types of leukocytes, including neutrophils, mast cells, eosinophils, lymphocytes, and T cells (a special kind of lymphocyte). All of these types of cells, and more, are involved in asthmatic inflammation. The immune cells release cytokines, regulatory proteins that act on other cells to direct their function. (In asthma, cytokines are also released by the cells lining the airways, the epithelial cells.) Cytokines have a number of effects: they increase blood flow to the affected site; cause fluid to leak into the affected tissue, creating swelling; and attract still more inflammatory cells into the area. READ MORE

This whole chain of events, called the inflammatory cascade, is an attempt to heal the injured tissue and/or rid your body of the invader. When healing is complete, inflammation normally subsides. LESS

PART 4 Inflamed Airways

What’s in a Word?

The term "asthma"...

In someone with asthma, the inflammation doesn’t subside. It becomes ongoing. The airways of people with asthma are chronically infiltrated with lymphocytes, eosinophils, and mast cells. Small airways, those less than 2 micrometers in diameter, are major targets of inflammation, but larger airways and, possibly, alveoli (microscopic air sacs) may be involved as well. The tissues of the airways become hypersensitive to even slight triggers. This chronic inflammation, if untreated, may lead to permanent changes in the physical structure of the airways.