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(ĭm″or-ăl′ĭ-tē) The ability of some cells, particularly cancer cells, to reproduce indefinitely. Normal human cells have a finite life expectancy. They may divide for a few dozen generations, but eventually stop reproducing and die.

immortal time bias

A bias in clinical research resulting from the observation that people who live long enough to enter a treatment trial may have less severe disease or greater resistance to disease than patients who don't qualify for the investigational therapy.

immotile cilia syndrome

(ĭ-mōt′ĭl, -mō′tīl″) An autosomal recessive condition characterized by severely impaired movement of the cilia or flagella of respiratory tract epithelial cells, sperm cells, and others. Affected cells lack the protein dynein, which is essential for effective ciliary motion. SYN: primary ciliary dyskinesia. SEE: dynein; Kartagener's syndrome.


(i-mūn′) [L. immunis, exempt, free from, safe] Protected from or resistant to a disease or infection as a result of the development of antibodies or cell-mediated immunity.

immune competence

The ability of the immune system (antibodies, T cells, and other elements) to respond to foreign antigens successfully. SEE: immunocompromised.

immune globulin

SEE: under globulin.

immune-mediated inflammatory reaction

The process by which the immune system destroys, dilutes, or walls off injurious agents and injured tissue. Small blood vessels dilate and become permeable. This increases blood flow and permits exudation of plasma and leukocytes. The cells arriving from the blood include monocytes, neutrophils, basophils, and lymphocytes; those of local origin include endothelial cells, mast cells, tissue fibroblasts, and macrophages. Other mediators of inflammation include cytokines, interleukins, and neuropathies.

immune reaction

1. A demonstrated antigenic response to a specific antibody. 2. The specific reaction of host cells to antigenic stimulation. SEE: immune response.

immune reconstitution inflammatory syndrome

ABBR: IRIS. A temporary clinical deterioration of a patient with HIV/AIDS occurring after the initiation of effective treatment with highly active antiretroviral therapy (HAART).

immune system

The lymphatic tissues, organs, and physiological processes that identify an antigen as abnormal or foreign and prevent it from harming the body. The body is protected from pathogen invasion by the skin, mucosa, and normal flora of the gastrointestinal tract and skin; chemicals contained in tears; the sebaceous glands; gastric acid; and pancreatic enzymes. The bone marrow produces white blood cells (WBCs), the body's primary internal defense. Lymphoid tissues, including the thymus gland, spleen, and lymph nodes, influence the growth, maturation, and activation of WBCs; lymphoid tissue in the gastrointestinal and respiratory tracts and mucous membranes contain WBCs for site-specific protection. Finally, physiologically active protein mediators, called ...

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