Human Anatomy & Physiology (9th Edition)

Published by Pearson
ISBN 10: 0321743261
ISBN 13: 978-0-32174-326-8

Chapter 21 - The Immune System: Innate and Adaptive Body Defenses - Review Questions - Page 799: 16

Answer

Interferons are a type of cytokine that modulate immunological activity in certain cells. The stimulus for interferon (IFN) production is infection-- usually viral, but also bacterial. Interferons are secreted to warn and protect uninfected neighbor cells, not to save the infected cells themselves. When the infected cells are dying, they bind to adjacent cells and promote the generation of a second messenger molecule in the uninfected cell. The second messenger alerts the uninfected cells to the danger of infection and promote the following antiviral actions: Break-up of invading viral RNA Prevention of viral replication Activation of NK cells and macrophages that destroy infected cells and prevent liberation of viruses from newly infected cells. There are two groups of IFN molecules-- Type I includes Interferon-beta (IFN-B), and interferon - alpha (IFN-A). Interferon gamma is a Type 2 interferon.. Type I interferons are secreted by viral-infected cells of various types--leukocytes and fibroblasts. IFN-gamma is produced mainly by lymphocytes.

Work Step by Step

Viruses do not have the organelles necessary to produce proteins. Consequently, they propagate by entering cells , taking over their protein replication machinery and employing the infected cells to make many replicas of the infecting virus. When the infected cells burst they liberate many copies of the infecting virus--so the infection spreads. Interferons are types of innate defense molecules that oppose (or interfere wit viral infection and replication. Cells that become infected with viral pathogens usually cannot save themselves, but they secrete interferon molecules that warn neighboring cells of the danger of infection; they also help their uninfected neighbors protect themselves against deadly infection by the viral and other pathogens. They enable uninfected cells to lyse viral RNA, and prevent viral replication. Interferons also activate natural killer cells (NK) and macrophages. These activated cells are able to prevent the spread of the infection by destroying newly infected cells Genetically engineered interferons (IFN-gamma) have been used in the treatment of viral diseases like hepatitis C, Karposi's sacroma ( associated with AIDS), genital warts, and malignant melanoma.
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