Chapter 42 Immunology

Chapter 42 Immunology - Nonspecific defense systems Animals...

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Unformatted text preview: Nonspecific defense systems Animals have various means of defense against pathogens agents that cause disease. Nonspecific defenses are general and act rapidly. They include 1. Barriers such as skin , as bacteria, fungi, and viruses can rarely penetrate healthy unbroken skin. And, mucus in the nose and respiratory tract traps microorganisms. And, cilia continuously move the mucus plus debris up towards nose and mouth. 2. Cells: Phagocytes . Even the normal flora the bacteria and fungi that usually live on body surfaces. They compete with pathogens for nutrients and space. 3. Chemical defenses. Mucous membranes produce defensins , peptides with hydrophobic domains that insert into the plasma membrane of the pathogen and make it permeable. Tears, nasal mucus, and saliva have an enzyme, lysozyme , that attacks bacterial cell walls. If pathogens reach digestive tract they may be killed by gastric juices or by bile salts in the small intestine. In blood, the complement system and interferons . Nonspecific defenses: surface barriers Nonspecific cellular and chemical defenses Cellular components Phagocytes travel freely in the lymph and circulatory systems and may move out of vessels and into tissues. Foreign cells, viruses, and fragments become attached to the phagocyte membrane and are engulfed Other agents inside the phagocyte kill the pathogens Natural killer cells are a type of lymphocyte that can detect virus-infected cells and some tumor cells. Can initiate apoptosis in these cells Can interact with the specific defense mechanisms and lyse cells labeled by antibodies Complement system and inerferons Blood contains the complement system . These proteins act in a cascade: Each protein activates the next. The complement proteins provide three types of defense: 1. Attach to microbes and mark them for phagocytes to engulf. 2. Activate inflammation response and attract phagocytes to the site of infection. 3. Lyse invading cells Interferons are signaling molecules produced by cells infected by a pathogen. Interferons increase resistance of neighboring cells to the pathogen by: 1. binding to receptors on non-infected cell membranes and stimulating a signaling pathway that inhibits viral reproduction 2. stimulating cells to hydrolyze the pathogens proteins to peptides Inflammation Inflammation is a response to injury. Mast cells are cells adhering to skin and organ linings; release chemical signals: Tumor necrosis factor cytokine that kills target cells and activates immune cells Prostaglandins dilate blood vessels and interact with nerve endings, responsible for pain Histamine amino acid derivative that leads to itching and allergic reactions. More inflammation Symptoms of inflammation: Redness, swelling, heat, pain....
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This note was uploaded on 04/19/2011 for the course LS 2 taught by Professor Pires during the Spring '08 term at UCLA.

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Chapter 42 Immunology - Nonspecific defense systems Animals...

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