(sĕn‵sĭ-tĭ-zā'shŭn )

1. The production by B lymphocytes of specific antibodies and by T lymphocytes of specific cellular reactions to a foreign antigen. When the antigen is encountered again, an immune response occurs. The production of antibodies by B lymphocytes or the activation of T lymphocytes when an allergen is first encountered. When the allergen is encountered again, an abnormal immune response occurs.

   SEE: hypersensitivity..

2. The process of making a person susceptible to a substance by repeated injections of it. SYN: sensibilization..

active s.Sensitization produced by injecting an antigen into a susceptible person.

autoerythrocyte s.A syndrome characterized by the spontaneous appearance of painful ecchymoses, usually at the site of a bruise. The areas itch and burn. The condition is commonly associated with headache, nausea, vomiting, and occasionally with intracranial, genitourinary, and gastrointestinal bleeding. With few exceptions, the disorder affects women of middle age. The cause is assumed to be autosensitivity to a component of the red blood cell membrane. There is no specific therapy.SYN: purpura; psychogenic.

cross s.1The perception of pain in one organ (e.g., the urinary bladder) after experiencing pain in a neighboring organ (e.g., the bowel).2Allergic hypersensitivity to an antigen that resembles another.

passive s.Sensitization produced in a healthy person by injecting the person with the serum from a sensitized animal or human.

protein s.Sensitization as a result of previous injection of a foreign protein into the body.