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Idiopathic: A term applied to a disease for which the cause is unknown.

Ig: The abbreviation for immunoglobulin. It is usually followed by the type of immunoglobulin, for example IgG, IgM, IgA, IgD, IgE. Immunoglobulins G, M, and A are the three principal types of antibodies.

Iliac Crest: The edge of the hip bone from which marrow is usually sampled for diagnosis of blood cell diseases.

Immune Deficiency: Impaired ability of the body's defense mechanisms to combat infections by bacteria, viruses and fungi.

Immune Globulins or Immunoglobulins:

Immune Response: The reaction of the body to an antigen, for example an infectious agent or an immunization, or to the tissues of another individual as in an allogeneic transplant. (See Gamma Globulins)

Immune Thrombocythemia Purpura (ITP): A decrease in blood platelets as the result of the formation of anti-platelet antibodies. The disease can be associated with some lymphomas and Chronic Lymphocytic Leukemia. It usually occurs in the absence of an associated disease.

Immunoelectrophoresis: A test to separate plasma or urine proteins. The method can be used to identify monoclonal (abnormal) immunoglobulins. These proteins are important diagnostic features of myeloma and some lymphomas.

Immunofixation: A sensitive test to separate plasma or urine proteins and to identify monoclonal (abnormal) immunoglobulins.

Immunoglobulins: Proteins in the blood plasma which function as antibodies and play an important part in controlling infections.

Immunophenotyping: A method that uses the reaction of antibodies with cell antigens to determine a specific type of cell in a sample of blood cells, marrow cells, or lymph node cells. The antibodies react with specific antigens on the cell. A tag is attached to antibody so that it can be detected. The tag can be identified by the laboratory equipment used for the test. As cells carrying their array of antigens are tagged with specific antibodies they can be identified; for example, myelogenous leukemic cells can be distinguished from lymphocytic leukemic cells. Normal lymphocytes may be distinguished from leukemic lymphocytes. This method also helps to subclassify cell types, which may, in turn, help to decide on the best treatment to apply in that type of leukemia or lymphoma. The antigen on a cell is referred to as cluster of differentiation or “CD” with an associated number. For example, CD16 may be present on leukemic lymphoblasts and CD33 on leukemic myeloblasts.

Immunosuppression: A state in which the immune system does not function properly and its protective functions are inadequate. The patient is more susceptible infections, including from microbes that are usually not highly infectious (See Opportunistic Infection). This can occur as a result of intensive chemotherapy and radiation therapy, especially as used for conditioning of a patient for transplantation. It also can occur because of disease states. Human immunodeficiency virus infection can lead to immunosuppression. Graft versus host disease creates an immunosuppressive state in that immune protection against infection is inadequate. In the transplant patient, the conditioning regimen and severe graft versus host disease can combine to permit overwhelming infection.

In Vitro: A biological process made or facilitated to occur in a laboratory vessel or other controlled experimental environment rather than within a living organism or natural setting.

In Vivo: Literally in a living organism. Therefore, studies carried out in animals or humans may be referred to by this term.

Incidence: The number of newly diagnosed cases for a specific disease or group of diseases during a specific time period, usually a year. When expressed as a rate, it is the number of new cases during that time period per standard unit of population. E.g., 10 cases/100,000 population per year.

Indwelling Catheter: Several types of catheters can be used for patients receiving intensive chemotherapy or nutritional support. An indwelling catheter is a special tubing inserted into a large vein in the upper chest. The catheter is tunneled under the skin of the chest to keep it firmly in place. The external end of the catheter can be used to administer medications, nutritional fluids, or blood products or to withdraw blood samples. With meticulous care, catheters can remain in place for long periods of time (many months), if necessary. They can be capped and remain in place in patients after they leave the hospital and used for outpatient chemotherapy or blood product administration.

Intensification Therapy: The administration of anti-cancer drugs to a patient in remission after remission-induction treatment in an attempt to kill residual leukemia or lymphoma cells.

Interferons: A family of naturally-occurring proteins derived from human cells and involved principally in fighting viral infections. They are now available as products of genetic engineering for use in the treatment of leukemias, especially chronic myelogenous leukemia and in combination with other drugs some lymphomas.

Interleukin: see Cytokine

Interstitial Pneumonitis: A severe inflammation in the lungs that can occur as a toxic effect of total body irradiation in the conditioning regimen for transplantation. The small airways and intervening spaces between the air sacs get congested and swollen. The exchange of oxygen between inspired air and the blood flowing through the air sac linings can be compromised. Typically, no infection is present although a similar reaction can occur as a result of infection.

Intrathecal: This term means within the spinal canal, the space between the double-layered covering or lining of the brain and spinal cord. The lining is called the meninges. In some situation drugs have to be administered into the spinal canal when leukemia or lymphoma cells are on the meninges. This process is called intrathecal therapy.

Intravenous Infusion: The administration of antibiotics, blood products, anti-cancer drugs, or nutrient fluids into a patient's vein over a period of time.