Central Glossary

Adaptive immune response: Second line of the immune response that is specific to a given foreign molecule or pathogen and leads to an " immunological memory " after the first response to the molecule or pathogen. Additive: The effect when two or more agents act together to achieve a result that is the sum of the effects achieved by the individual agents. AIDS­defining illness or event: Any one of a group of illnesses presence of which indicates that a patient's HIV infection has progressed to the acquired immune deficiency syndrome (AIDS); these conditions include, among others, yeast infections of the airways (i.e., candidiasis), Kaposi's sarcoma, certain viral infections, tuberculosis, and certain cancers. Airway obstruction: Respiratory problem in which the small airways (bronchioles) show increased resistance, thereby reducing the amount of air inhaled in each breath and, consequently, the amount of oxygen that can be taken up into the body. Alveolus (pl. alveoli): Tiny airsac found in the mammalian lungs at the end of the air passages (bronchioles) that make up most of the lung tissue and which are the site of the oxygen and carbon dioxide exchange in the lungs; a human lung contains about 150 million alveoli. Anterior: Towards the front (e.g., the anterior region of the brain is located toward the front of the head). Antibody: A protein produced by the body's immune system to recognize and fight infectious organisms and other foreign substances that enter the body. Each antibody is specific to a particular piece of an infectious organism or other foreign substance. Antibodies develop after the first exposure to a substance. Antigen: Any substance considered foreign to the body that can stimulate the body to produce antibodies against it. Antiretroviral: A drug that interferes with the ability of a retro­ virus, such as HIV, to make more copies of itself. Antiretroviral therapy (ART): Medications for the treatment of infection by retroviruses and primarily is used to treat HIV. Apoptosis: Cell death in which the affected cell participates by activating a cascade of biochemical reactions that lead to death; also known as programmed cell death or cell suicide. Asthma: Chronic inflammation of the lungs and airways (bronchi and bronchioles), leading to a reversible narrowing of the airways and breathing difficulties. Atrial fibrillation: A type of abnormal heart rhythm (i.e., arrhythmia) that involves the upper chambers (i.e., atria) of the heart; characterized by quivering rather than coordinated contraction …