Acetylating enzyme: Enzyme that adds acetyl (CH3CO-) group to organic molecules Acetylcholine: A chemical found in vertebrate neurons that carries information across the synaptic cleft, the space between two nerve cells. Acquired immunity: A form of cellular defense, which identifies certain foreign substances (antigens) as harmful to the body. For this reason, the body can acquire resistance to a particular foreign agent. Actinic Keratosis: A lesion that is abnormally sensitive to ultraviolet light (sunlight) Thought to be a precancerpous lesion that is more common in fair-skinned or elderly individuals. It is sharply outlined, red or skin-colored, flat or elevated keratotic growth that may become cancerous. Active Process: An event in a cell that requires input of energy. Active Radical: An unstable molecular component produced by breakage of a bond. These radicals are very active and known to start chain reactions. Acute myeloid leukemia: Leukemia is a progressive malignant disease of the blood-forming organs, characterized by distorted proliferation and development of leukocytes (white blood cells) and their precursors in the blood and bone marrow. Leukemia is classified clinically on the basis of (1) duration and characteristic of the disease - acute or chronic; and (2) the type of cells involved - myeloid, lymphoid or monocytic. Adenocarcinoma: Carcinoma (malignant new growth of epithelial cells) derived from glandular tissue or the tumor cells may be arranged like a specific gland like ovary or may produce particular product of a gland. Adenoma: A benign epithelial tumor in which the cells form recognizable glandular structures or in which the cells are clearly derived from the glandular epithelium. Adenomatous: Pertaining to adenoma or to nodular hyperplasia of a gland. Adenopathy: A general term for glandular disease. Adenosine: A nucleoside, containing the purine base adenine covalently bound a ribose sugar. Adenosine Deaminase: A hydrolytic enzyme that catalyzes the reaction between adenosine and water producing inosine and ammonia. Amino group is removed from adenosine (A) to produce inosine (I). The reaction is a part of the purine salvage mechanism. A deficiency of this enzyme produced by genetic abnormality has been found in many individuals with severe combined immunodeficiency syndrome. Scientists are also trying to destabilize pathogens like HIV by creating single point mutations in their RNA genome where an A is mutated to become an I. Because an I looks very much like G (guanosine), as shown below, it forms IC base pairs which will lead to GC base pairs where C is cytosine in the next generation. Adenosine triphosphate: The nucleoside adenosine is attached through its sugar (ribose) group to three phosphate groups. This is a high energy phosphate, and privides the energy needed for bond forming and bond breaking reactions. Adiponectin: A protein hormone produced and secreted by adipocytes (fat cells). This hormone regulates lipid and glucose metabolism. It also affects the body’s response to insulin. Adjuvant: A substance that, when added to a medicine, speeds or improves its action. Adjuvant therapy: Treatment given in addition to initial therapy to help reach ultimate goal. Adoptive Immunotherapy: Immunotherapy in which natural cancer cell destroying activity is potentiated, for example in cellular mediated adoptive immunotherapy natural killer cells are stimulated by cytokine such as interleukin 2 (IL-2), administered to cancer patients to destroys tumor. Adrenals: These are endocrine glands situated above both kidneys and produce several hormones including estrogen and progesterone.