Acute - a descriptive term used to describe an illness, infection or symptom which is usually short in duration.

Adenoids (pharyngeal tonsil) - lymphoid tissue located in the upper part of the throat behind the nose.

Agammaglobulinemia - complete lack of immunoglobulins (antibodies) in the blood.

Antibodies - protein molecules that are produced and secreted by certain types of white cells (lymphocytes) in response to stimulation by an antigen. Their primary function is to fight bacteria, viruses, toxins, and other substances foreign to the body.

Antigen - any foreign substance that provokes an immune response when introduced into the body; the immune response usually involves both T-lymphocytes and B-lymphocytes.

Autoantibody - an antibody that reacts against a person's own tissue instead of against foreign substances.

Autoimmune Dis-ease - a dis-ease that results when the body's immune system reacts against a person's own tissue.

Autosome - any chromosome other than the sex chromosome.

Bacteria - single cell organisms (microorganisms) that is capable of being observed only under a microscope. While some bacteria are capable of being useful, many bacteria are capable of symptomatically causing dis-ease in humans.

B-cell (B-lymphocytes) - white blood cells of the immune system derived from bone marrow and involved in the production of antibodies.

Bone marrow - soft tissue located in the hollow centres of most bones that contains developing red blood cells and cells of the immune system.

Bronchiectasis - a dilation of the tubes (bronchi) leading to the air sacs of the lung; this usually is the consequence of recurrent infections.

Chronic - descriptive term used to describe an illness or infection, which may be recurrent or lasting a long time.

Complement - a complex series of blood proteins that act in a definite sequence to effect the destruction of bacteria, viruses and fungi.

Epitope - a characteristic shape or marker on an antigens surface.

Erythrocyte (red blood cell, BC) - a very small circular biconcave cell produced in the bone marrow and found in the blood stream; contains hemoglobin, which carries oxygen to body tissues.

Fungus - member of a class of relatively primitive microorganisms including mushrooms, yeasts, and molds.

Granulocyte - a white cell of the immune system characterized by the ability to ingest (phagocytize) foreign material. A granulocyte is identified under the microscope by the presence of many granules. Neutrophils, eosinophils and basophils are examples of granulocytes.

Helper T-cells - a subset of T-cells that assist B-cells and T-cells to function more optimally.

Histocompatibility tests - immunologic tests for comparing the antigens on the tissue of a transplant donor with those of the recipient. The more closely matched, the improve the chance for the transplant to take.

Hypogammaglobulinemia - lower than normal levels of immunoglobulins (or antibodies) in the blood.

IgA - an immunoglobulin found in blood, tears, saliva, and in the mucous membranes of the respiratory and intestinal tracts.

IgD - an immunoglobulin whose function is inadequately understood at this time.

IgE- an immunoglobulin found in trace amounts in the blood and considered to be responsible for allergic reactions.

IgG - the most abundant and common of the immunoglobulin.IgG functions mainly against bacteria and some viruses. It is the only antibody that is capable of crossing the placenta.

IgM - an immunoglobulin found in the blood. IgM functions in much the same way as IgG though is formed earlier in the immune response. It is also very efficient in activating complement.

Immune response - the activity or response of the immune system against foreign substances.

Immunocompetent - capable of developing an immune response.

Immunodeficiency -a state of either a congenital (present at birth) or an acquired abnormality of the immune system, which prevents adequate immune responsiveness.

Immunoglobulin (abbreviation Ig) - another name for antibody; there are five major classes: IgA, IgD, IgG, IgM, and IgE.

Immunosuppression - the process of diminishing the immune response, usually accomplished with strong medicine and used in the treatment of autoimmunity and organ transplantation.

In vitro - outside of a living environment refers to a process or study-taking place in test tubes, etc.

In vivo - in the intact animal, usually refers to a process or study, which takes place in a living animal.

Leukocyte (white blood cell, WBC) - a group of small colorless blood cells, which play a major role in the body's immune system. There are five basic white blood cells: monocytes, lymphocytes, neutrophils, eosinophils and basophils.

Lymph - a transparent, slightly yellow fluid containing primarily lymphocytes. Lymph is composed of tissue fluids collected from all parts of body and returned to the blood via the lymphatic vessels.

Lymph nodes - small bean-sized organs of the immune system, distributed widely throughout the body. Each lymph node contains a variety of specialized compartments which house B-cells; T-cells, and macrophages lymph nodes unite in one location the several factors needed to produce an immune response.

Lymphocytes - Small white cells, normally present in the blood and in lymphoid tissue, that bear the major responsibility for carrying out the functions of the immune System. There are two major forms of lymphocytes, B-cells and T-cells, which have distinct though related functions in generating an immune response.

Lymphokines - substances Produced and released by T-lymphocytes which enhance the function of other cells of the immune system.

Macrophage - a phagocytic cell found in the tissues, able to destroy invading bacteria or other foreign material. (see Monocyte)

Major histocompatibility complex - an important region on the 6th chromosome in man, which in general controls the transplant rejection responses, and also the intensity of the immune response in general.

Metabolism - a general term which summarizes the chemical changes within a cell, which result in either the building up or breaking down of living material.

Metabolite - a substance, which is either acted upon or produced in the process of metabolism.

Microbes - minute living organisms, usually one-cell organisms, which include bacteria, protozoa, and fungi.

Microorganism - check microbes.

Molecule - the smallest unit of matter of an element or compound.

Monocyte - phagocytic cell found in the blood that acts as a scavenger capable of destroying invading bacteria or other foreign material; these cells develop into macrophages in tissues.

Monokines - Powerful chemical substances that are secreted by monocytes and macrophages and help direct and regulate the immune response.

Neutrophil - a type of granulocyte, found in the blood and tissues that are capable of ingesting microorganisms.

Opportunistic infection - an infection in immune deficient, or immune-suppressed persons, symptomatically caused by organisms that do not usually affect people with deemed normal immune systems.

Organism - individual living thing.

Parasite - a plant or animal that lives, grows, and feeds on or within another living organism.

Phagocytes - a general class of white blood cells that ingest microbes or other cells and foreign particles. Monocytes, macrophages and neutrophils are types of phagocytes.

Plasma cells - antibody producing cells descended from B-cells.

Platelet (thrombocyte) - smallest and most fragile of the blood cells; primary function is associated with the process of blood clotting.

Prophylactic - medical therapy initiated to prevent or guard against dis-ease and infection.

Protein - a class of chemicals found in the body made up of chains of amino acids (building blocks). Immunoglobulins (antibodies) are proteins.

Spleen - an organ in the abdominal cavity. It is an important site of antibody production and like lymph nodes contains B-cells, T-cells and macrophages.

Stem cells - cells from which all blood cells and immune cells are derived.

Suppressor T-cells - a subset of T-cells that turn off antibody production by B-cells.

T-cells (or T-lymphocytes) - lymphocytes that are processed in the thymus, an organ in the chest. They are responsible, in part, for carrying out the immune response.

Thymus gland - a lymphoid organ located behind the upper portion of the sternum (breastbone). The thymus is the chief educator of T-cells. This organ increases in size from infancy to adolescence, and then begins to shrink.

Tolerance- a state of non-responsiveness to a particular antigen in the face of the ability to demonstrate an adequate immune response to other antigens.

Tonsils - two oval-shaped masses of lymphoid tissue situated on each side of the back of the mouth, leading to the throat.

Virus - submicroscopic microbe causing infectious dis-ease. Is only capable of reproducing in living cells.