Protective enzyme has a downside: Asthma.An enzyme whose natural job may be to ward off fungi and parasites contributes to the lung inflammation characteristic of asthma, a new study concludes. The enzyme is known as a chitinase because it breaks down the complex sugar chitin, a tough molecule found in the cell walls of fungi, the surface of parasitic worms, and the exoskeletons of insects and crustaceans. Mammals don't make chitin, but people have many genes encoding chitinases, so biologists consider the enzymes to be part of the human immune response immune response n. An integrated bodily response to an antigen, especially one mediated by lymphocytes and involving recognition of antigens by specific antibodies or previously sensitized lymphocytes. . Jack A. Elias of Yale University Yale University, at New Haven, Conn.; coeducational. Chartered as a collegiate school for men in 1701 largely as a result of the efforts of James Pierpont, it opened at Killingworth (now Clinton) in 1702, moved (1707) to Saybrook (now Old Saybrook), and in 1716 was Medical School in New Haven New Haven, city (1990 pop. 130,474), New Haven co., S Conn., a port of entry where the Quinnipiac and other small rivers enter Long Island Sound; inc. 1784. Firearms and ammunition, clocks and watches, tools, rubber and paper products, and textiles are among the many and his colleagues have now found that mice given a substance that triggers asthmalike lung inflammation produce large amounts of a chitinase in their lungs, the researchers report in the June 11 Science. Blocking the enzyme with an antibody or another compound decreases the inflammation. Elias' team further discovered that lung-tissue samples from asthmatic people, but not samples from other people, contain significant amounts of the chitinase. Some researchers have suggested that asthma is on the rise because people living in developed countries now face fewer parasitic infections than people did in the past. According to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. this hypothesis, if the immune system immune system Cells, cell products, organs, and structures of the body involved in the detection and destruction of foreign invaders, such as bacteria, viruses, and cancer cells. Immunity is based on the system's ability to launch a defense against such invaders. isn't properly trained during childhood, it may overreact o·ver·re·act v. To react with unnecessary or inappropriate force, emotional display, or violence. to innocuous allergens in the lungs, causing asthma (SN: 8/26/00, p. 134). A chitinase's presence in uninfected lungs of asthma patients supports this hypothesis. |
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