Blood Health Article

Sickle cell anemia

Sickle cell anemia is an inherited disorder caused by a defect in one of hemoglobin's four protein chains. The defective hemoglobin distorts the shape of the red blood cells and injuries the red blood cell membrane. Water and potassium leak from the cells, causing the red blood cells to become rigid and "sickle-shaped." As a result of these changes, oxygen transport is severely interrupted and circulation of the blood through the blood vessels can become blocked. These irregular blood cells do not carry as much oxygen as their normally shaped counterparts. Although the prognosis for individuals with sickle cell anemia was historically poor, improvements in life expectancy and quality have been made due to early diagnosis and treatment.

Hemophilia

Hemophilia is hereditary group of bleeding disorders that results in insufficient clotting and excessive bleeding. Types are hemophilia A, hemophilia B, and von Willebrand's disease. Hemophilia A is the most common type. It results from a deficiency in clotting factor VIII. Only males have this sex-linked disease, but women may be carriers. Uncontrolled bleeding, both internal and

external, may be caused by the smallest of injuries. Treatment involves clotting factor supplementation, and tranfusions are common when blood is lost, or prophylactically.

Human immunodeficiency virus

Human immunodeficiency virus (HIV), the causative agent of acquired immune deficiency syndrome (AIDS), attacks and kills T lymphocytes. This dis-ease cripples the immune system and leaves the body helpless to stave off infections. As AIDS progresses, the number of helper T lymphocytes drops from a normal 1,000 per cubic millimeter to below 200.

KEY TERMS

Aerobic metabolism—Metabolic processes that require oxygen.

Antibody—An immune protein that marks foreign microorganisms in the body for destruction by other immune cells.

Antigen—A protein that is attached to a cell's plasma membrane.

Centrifugation—A laboratory procedure in which a test tube of blood or other liquid is spun at a high speed.

Clotting factor—A set of substances released by platelets that function in the clotting mechanism.

Electrolytes—The salts and other substances present in the plasma that function in crucial body processes.

Fibrin—A protein that functions in the clotting mechanism; forms mesh-like threads that trap red blood cells.

Fibrinogen—The inactive form of fibrin present in plasma; activated by clotting factors released by platelets.

Hemoglobin—The protein found in red blood cells that binds oxygen; consists of four protein chains surrounding an iron core.

Hemophilia—A genetic disorder in which one or more clotting factors are not released by the platelets; causes severe bleeding from even minor cuts and bruises.

Hemopoiesis—The process of red blood cell formation in the bone marrow.

Histamine—A chemical released by basophils during the inflammatory response; causes blood vessels to dilate.

Immunoglobin—An antibody.

Inflammatory response—A type of non-specific immune response; involves the release of chemicals from basophils that increase blood circulation and white blood cell migration to the affected area.

Interstitial fluid—The fluid that bathes cells.

Lymph node—A small structure located at several points in the body; consists of lymphatic tissue that filters blood and removes microorganisms.

Lymphocyte—A type of white blood cell; includes B and T lymphocytes.

Lysozyme—An enzyme released by neutrophils that kills cells.

Lymphoid stem cell—The cell from which B and T lymphocytes are derived.

Phagocytize—To engulf and digest a cell.

Plasma cell—The cell derived from the B lymphocyte, which secretes antibodies.

Pluripotent stem cell—The type of stem cell from which red blood cells and more white blood cells are derived in the bone marrow.

Sickle cell anemia—A genetic disorder caused by a defect in one of hemoglobin's four protein chains; causes red blood cells to be sickle-shaped.

BOOKS

Long, Michael W. and Max S. Wicha, eds. The Hematopoietic Microenvironment: The Functional and Structural Basis of Blood Cell Development. Baltimore: Johns Hopkins University Press, 1993.

Shin, Linda, and Karen Belliner. Blood and Coagulation Disorders Sourcebook: Basic Information about Blood and Its Components. Omnigraphics, 1998.

PERIODICALS

Creteur, Jacques, William Sibbald, and Jean-Louis Vincent. "Hemoglobin Solutions: Not just Red Blood Cell Substitutes." Critical Care Medicine 28 (August 2000): 3025-34.

Delves, P. J. and I. M. Roitt. "The Immune System: First of Two Parts." New England Journal of Medicine 343 (6 July 2000): 37-49.

Delves, P. J. and I. M. Roitt. "The Immune System: Second of Two Parts." New England Journal of Medicine 343 (13 July 2000): 108-17.

Tremper, Kevin K. "Perfluorochemical Blood Substitutes: Indications for an Oxygen-Carrying Colloid." Anesthesiology 91 (November 1999): 1185.

ORGANIZATIONS

American Sickle Cell Anemia Association. 10300 Carnegie Avenue, East Office Building (EEb18), Cleveland, OH44106. (216) 229-8600. <http://www.ascaa.org>.

America's Blood Centers. 725 15th Street NW, Suite 700, Washington, DC 20005. (202) 393-5725. <http://www.americasblood.org>.

National Hemophilia Foundation. 116 West 32nd Street, 11th Floor, New York, NY 10001. (800) 42-HANDI. <http://www.hemophilia.org>.