B-cell: A type of lymphocyte normally involved in the production of antibodies to combat infection. It is a precursor to a plasma cell (A terminally differentiated antibody forming and usually antibody secreting, cell of the B-cell lineage). During infections, individual B-cell clones multiply and are transformed into plasma cells, which produce large amounts of antibodies against a particular antigen on a foreign microbe. This transformation occurs through interaction with the appropriate CD4 T-helper cells. B-lymphocytes or B cells: One of the major types of cells present in the immune system. They synthesize protein factors known as antibodies in response to antigens, which are secreted outside the cells. Bacteremia: Presence of bacteria in the blood. Barrett’s syndrome: Peptic ulcer of the lower esophagus. Basal Cells: Small proliferating layer of cells present in the lower part of the epidermis. Basement membrane: The delicate layer of extracellular condensation of mucopolysaccharides and proteins underlying the epithelium of mucous membrane between two cells. BCG: Bacille Calmette-Guerin, a strain of Mycobacterium bovis, which was made avirulent by culturing for many years on a medium enriched in beef bile. Bcl-2: A proto-oncogene, activated by chromosome translocation in human B-cell lymphomas (hence bcl). Encodes a plasma membrane protein. The gene product inhibits programmed cell death (apoptosis) and is homologous with the worm gene ced 9. Benign tumor: Tumors produced from one kind of cells or mixture of cells; they grow and become large within the tissue of origin and do not spread to other part of the body. Beta-Lactamase: A hydrolytic enzyme that catalyzes the reaction between lactam - a cyclic amide - and water. A group of enzymes with this activity act on penicillins and cephalosporins to inactivate them. bFGF: Basic fibroblast growth factor, one of the two founder members of a family of structurally related growth factors for mesodermal or neuroectodermal cells. Bile acids: Steroid derivatives with carboxyl-containing side chain. The principal bile acids are cholic and chenodeoxycholic acids. They form powerful detergent, the bile salts, by reacting with amino acid glycine and a strong organic acid taurine. Biliary tract: Bile duct. Biofeedback: The process of furnishing an individual information, usually in an auditory or visual mode, on the state of one or more physiological variables such as heart rate, blood pressure, or skin temperature; such a procedure often enables the individual to gain some voluntary control over the physiologic variables being sampled. Biological Modifiers: Agents, either natural or synthesized that increase or restore normal immune system such as interferons, interleukins, monoclonal antibodies. Biomarker: A specific biochemical in the body, which has a particular molecular feature that makes it useful for measuring the progress of disease or the effects of treatment. Biopsy: Removal of a piece of body tissue for the purpose of laboratory analysis to establish diagnosis. Biotherapy: Therapy that uses biological agents such as antibodies and cytokines. Blast crisis: In patients with chronic myelogenous leukemia, the progression of the diseases to an acute advanced phase, evidenced by an increased number of immature white blood cells in the circulating blood. Sometimes loosely used to describe a rapid increase in the white blood cell count of any leukemia patient. Blastocyte: An embryonic cell that has not yet become differentiated. Blasts: Blast cells, the least differentiated blood cell without commitment to the particular series. Bleomycins: A mixture of glycopeptide antibiotics produced by a strain of Streptomyces verticillus. They bind to DNA causing chain scission and removal of purine and pyrimidine bases, resulting in inhibition of DNA synthesis and accumulation of cells in G2 phase in the cell cycle. Blood-brain barrier: A protective barrier formed by the blood vessels and glia (supportive tissue) of the brain. It prevents some substances in the blood from entering brain tissue. Bloom's syndrome: An autosomal recessive syndrome developing during infancy consisting of permanent dilatation of blood vessels on the face creating small focal red lesions, photosensitivity, and dwarfism. Abnormalities in chromosome structures and in immunoglobulins are present, and there is a high incidence of malignancy, especially leukemia. BMI (Body mass index): A key index for relating a person's body weight to their height. BMI is a person's weight in kilograms (kg) divided by their height in meters (m) squared. The National Institute of Health (NIH) now defines normal weight, overweight, and obesity according to the BMI. According to NIH obesity is defined as BMI over 30. However, some very muscular person may have high BMI without any health risk. Bolus: A concentrated mass of pharmaceutical preparation given intravenously could also be referred to a rounded mass of food ready to swallow. Bone marrow: The soft, spongy material in the center of bones that produce blood cells. Brachytherapy: In radiotherapy, treatment with ionizing radiation whose source is applied to the surface of the body or is located a short distance from the body area being treated. BRCA1: A tumor-suppressing gene; even if one copy of it is damaged, cancer can develop. Certain mutations confer a high probability (85% lifetime risk) of developing breast cancer, and other types cause ovarian cancer. Familial mutations of this gene are particularly common among people in the Ashkenazi Jewish ethnic group. Bromodeoxyuridine: A thymidine analog with bromine at the 5-position. In the diagram below, on the left is thymidine 5' phosphate (5'-TMP), and on the right is bromodeoxyuridine 5' phosphate. . Burkitt’s Lymphoma: A form of undifferentiated malignant lymphoma, usually found in central Africa, but also reported from other areas. The Epstein-Barr virus, a herpes virus, has been isolated from this lymphoma, and has been implicated as a causative agent. Butyrate: Salt of butyric acid, a 4-carbon saturated monocarboxylic acid, CH3-CH2-CH2-CH2-COOH..