Immun System/PART 1
Immunity (medical) : resistance of an organism to infection or disease
Immunity involves both specific and non-specific components.
Periodontal diseases: initiated and sustained by factors or substances produced by the subgingival microbiata
n Directly injury host cells and tissues
n Secondary damage the tissues through the activation of inflammatory or immunologic systems
Microorganisms produce:
1-solubleenzymes
2-nutrients for their growth
3- metabolic waste products
n Proteinase capable of digesting: collagen, elastin, fibronectin, fibrin
n Argl-protease produce by P.gingivalis to induce astrong humoral response
n Leukotoxins produce by Actinobacillus Actinomyces Temcomitance has capacity to kill leukocytes
n Lipopolysaccharide(LPS) of gram negative bacteria capable of involving both inflammatory and
immunologic responses
n Lipothetic acid(LTA) of gram positive bacteria activate chemical mediators of inflammatory process to
induce vesicular permeability and encourage through chemotactic action the
inflammatory cell to move into the tissue and involve defence cell to release
pro inflammatory agents and cytokines
Immunological reactions play an essential role in pathogenesis of gingival and periodontal disease
There are four type of reaction
Type 1 : anaphylactic reaction
Type 2 : cytotoxic hypersensitivity
Type 3 : Arthrus hypersensitivity
Type 4 : Delayed hypersensitivity (cell-mediated
Host defense processes
Divided into :
1- Innate or non specific response
2- Adaptive or specific response
1- Innate or non specific response
The innate immune system comprises the cells and mechanisms that defend the host from infection by other organisms, in a non-specific manner. This means that the cells of the innate system recognize and respond to pathogen in a generic way, it does not confer long-lasting or protective immunity to the host. Innate immune systems provide immediate defense against infection.
The major functions of the innate immune system include:
• •Recruiting immune cells to sites of infection, through the production of chemical factors, including specialized chemical mediators, called cytokine.•Activation of the complement system to identify bacteria, activate cells and to promote clearance of dead cells.The identification and removal of foreign substances present in organs, tissues, the blood and lymph, by specialized wbc .
• Activation of the (AIS )through a process known as antigen presentation.
Inflammation
it’s one of the first responses of the immune system to infection or irritation. Inflammation is stimulated by chemical factors released by injured cells, and to promote healing of any damaged tissue following the clearance of pathogens.Chemical factors produced during inflammation (histamine, braycanine,serotonin and prostaglandin and attract phagocytes, especially neutrophils).[
Complement system
helps, or “complements”, the ability of antibodies to clear pathogens or mark them for destruction by other cells. The cascade is composed of many plasma proteins, synthesized in the liver, primarily by hepatocyts. The proteins work together to:
• trigger the recruitment of inflammatory cells.
• •"tag" pathogens for destruction by other cells BY opsonization, or coating, the surface of the pathogen.disrupt the plasma membrane of an infected cell, resulting in cytolysis of the infected cell, causing the death of the pathogen.
Mast cells
Mast cells are a type of innate immune cell that reside in connective tissue and in the mucous membranes. They are intimately associated with defense against pathogens and wound healing, but are also often associated with allergy and anaphylaxis . When activated, mast cells rapidly release characteristic granules, rich in histamine , along with various hormonal mediators, an chemotactic cytokine into the environment. Histamine dilates blood vessile, causing the characteristic signs of inflammation, and recruits neutrophils and macrophages.
Macrophages
Macrophages, from the Greek, meaning "large eaters," are large phagocytic leukocytes, which are able to move outside of the vascular system by moving across the cell membrane of capillary vessels. In tissues, organ-specific macrophages are differentiated from phagocytic cells present in the blood called monocyts. Macrophages are the most efficient phagocytes, and can phagocytose substantial numbers of bacteria or other cells or microbes.The binding of bacterial molecules to receptors on the surface of a macrophage triggers it to engulf and destroy the bacteria. Pathogens also stimulate the macrophage to produce chemokines (such as collagenases ,proteases and lysosomal hydrolases).
A neutrophil
Neutrophils, along with two other cell types; eosinophils and basophils are known as granulocyte or as polymorphonuclear cells (PMNs).and it’s the first line of defense against all forms of injuries. Neutrophil granules contain a variety of toxic substances that kill or inhibit growth of bacteria and fungi. Similar to macrophages. The primary protective function are engulf,kill and digest by subustanses such as lysosymes , hyrolases and collagenases . Neutrophils are the most abundant type of phagocyte, normally representing 50 to 60% of the total circulating leukocytes, and are usually the first cells to arrive at the site of an infection. The bone marrow of a normal healthy adult produces more than 100 billion neutrophils per day.
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .