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B-cell Lymphomas: A large group of lymphoma sub-types that are composed of malignant T-cells with features of B-lymphocytes.
B-Lymphocyte: One of three specialized lymphocyte types. B-lymphocytes transform into plasma cells and produce antibodies in response to foreign substances such as bacteria, viruses, and fungi. B-lymphocytes are a vital part of the immune system and are important to our defense against infection. B-cells received their name from a structure called the Bursa of Fabricius in birds, which was found to be the source of antibody-producing lymphocytes. In humans, the bone marrow may be the equivalent of the bursa. Thus, in humans, “B” can be thought of as indicating that the lymphocytes are derived initially from the bone marrow.
BCR: The gene on chromosome 22 that is disrupted by the formation of the Philadelphia chromosome. The translocated ABL gene from chromosome 9 fuses with the remaining portion of the reciprocally translocated BCR gene to form a fusion oncogene BCR-ABL. This change is the molecular hallmark of CML and the protein encoded by the fusion gene is the seminal transforming event in the malignant transformation of the pluripotential lymphohematopoietic cell in the marrow that leads to the leukemia.
Bacteria: Microscopic organisms that are ubiquitous in nature. They normally inhabit the skin, mouth and nose, and lower intestines. Many types do not cause disease in healthy subjects. Some have a greater propensity to be disease-causing, especially if natural defenses are weakened by disease or cytotoxic treatment.
Beta 2-Microglobulin: A small protein molecule on the cell surface that determines tissue type or HLA type. The beta 2-microglobulin is shed from cells and enters the plasma. It can be measured in the plasma and reflects the number of myeloma cells in the patient. It is used as one of several prognostic indicators in myeloma. A very low level is better than a very high level.
Biopsy: A procedure to obtain tissue for diagnosis of an apparent abnormality. In many cases, a special needle can be used to obtain the tissue. In some cases, a larger piece of tissue may be removed surgically. Since the appearance of a lymph node is important in categorizing the type of lymphoma that may be present, surgical removal of an entire, enlarged lymph node or nodes is sometimes preferable (lymph node biopsy). The tissue is placed in preservative, stained with dyes, and examined under a microscope by a pathologist.
Blast T-cells: This term refers to the earliest marrow cells identified by the light microscope. Blasts represent about 1 percent of normally developing marrow cells. They are largely myeloblasts, which are cells that will develop into neutrophils. In normal lymph nodes, blasts are lymphoblasts, that is, cells that are part of lymphocyte development. In the acute leukemias, blast T-cells, similar in appearance to normal blast T-cells, accumulate in large numbers, perhaps up to 80 percent of all marrow cells. In acute myelogenous leukemia, myeloblasts accumulate and in acute lymphoblastic leukemia, lymphoblasts accumulate. Sometimes the distinction between myeloblasts and lymphoblasts can be made by examination of stained marrow cells through the microscope. Often, immunophenotyping or use of special staining of marrow cells is required to be sure of the distinction.
Blood Cells: There are three main types of cell in the blood: red cells that carry oxygen, white cells that principally prevent or combat infections, and platelets that help prevent bleeding. There are several types of white cell in the blood. Each cell type is represented in blood in the numbers that meet the functions they serve. One fluid ounce of blood contains about 150 billion red cells, 8 billion platelets, and 20 million white cells. Red cells live for months, platelets for a week or two, and white cells for a few days. The marrow must replace over 200 million cells removed from the blood each day.
Blood Count: A laboratory test requiring a small blood sample with which to measure the number and types of cells circulating in the blood. The term complete blood count or CBC is often used to refer to this test.
Bone Marrow: The bones are hollow and their central cavity is occupied by marrow, a spongy tissue that is the site of blood cell formation. By puberty, the marrow in the spine, ribs, breastbone, hip, shoulders, and skull is most active in blood cell formation. In the adult, the bones of the hands, feet, legs and arms do not contain marrow in which blood cells are made. In these sites, the marrow is filled with fat T-cells. When marrow cells have matured into blood cells they enter the blood that passes through the marrow and are carried throughout the body.