non-specific defense mechanisms
DESCRIPTION
Non-specific defense mechanisms. 1st line- skin and mucous Cilia lined trachea, hairs in pathways 2nd line- phagocytic WBC antimicrobial proteins (compliment & interferon) inflammatory response. Phagocytic WBC. Neutrophils (60-70% of all WBC) - PowerPoint PPT PresentationTRANSCRIPT
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Non-specific defense mechanisms
• 1st line- skin and mucous– Cilia lined trachea, hairs in pathways
• 2nd line- – phagocytic WBC– antimicrobial proteins (compliment & interferon)– inflammatory response
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Phagocytic WBC
• Neutrophils (60-70% of all WBC)• attracted by chemical signals from damaged cells and enter
tissues
• Monocytes (5% of all WBC)– develop into macrophages which use psudopodia to
capture invading bacteria
• Eosinophils (1.5% of all WBC)– used to attack bigger invaders “worms”
• natural killer cells – attack virus-infected cells to prevent spreading
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Antimicrobial proteins
• Compliment – various proteins in the plasma that work with antibodies, phagocytes, and on their own non-specifically to enhance immune response.
• interferon-proteins secreted by virus-infected cells. Inhibits virus reproduction in neighboring cells. Can be mass produced now and may be used to treat cancer patients.
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Inflammatory response• 1. Damaged tissues release chemical signals such as
histamine (contained in basophils WBC and mast cells of connective tissue) and prostaglandins to increase blood flow.
• 2. Prostaglandins induce vasodilation and increased permeability to clotting factors.
• 3. Chemokines release chemicals that mediate the arrival of phagocytic cells to the area
• Phagocytes consume debris and pathogens forming pus• Sometimes allergies cause massive release of histamine to
“safe” invaders, so antihistamines block this response
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Specific defense (3rd line)• Four major features
– Specificity (recognize particular antigens)– diversity (responds to millions of different invaders)– self/nonself recognition- – memory - acquired immunity so the second time
body is infected the response will be quick enough to avoid serious infection. This is the basis for vaccination.
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Cell surface markers
• Blood cells A, B, and Rh Factor proteins• Major histocompatibility complex (MHC) are
glycoproteins marking cell as self• MHC class I are on all nucleated cells• MHC class II are only on specific immune cells• These allow cytotoxic T-cells (MHC I) and helper
T-cells (MHC II with antigen fragments attached) to bond to cells
• Huge amount of variety, so each individual is unique in their MHC proteins.
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Humoral immunity
• Results in production of antibodies– Free antigens activate B- cells– B- cells make the antibodies and then develop
into Plasma cells and memory B-cells for next time
– Plasma cells secrete antibodies– antibodies attach to antigens making them easy
“prey” for phagocytes and complement
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Formation of lymphocytes
• Lymphocytes are WBC formed in the bone marrow. (B and T cells)
• B- cells fully develop in the bone marrow before being released
• T - cells then travel to the the thymus for further development before leaving.
• In the thymus they pick up recognition of MHC complex as self.
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Cell-mediated immune response• Antigens displayed by MHC class I glycoproteins in
infected cells activate Cytotoxic T cells
• Cytotoxic T cell give rise to memory T cells and Active cytotoxic T cells
• Activated cytotoxic T cells attack cells by binding to and lysing them
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2nd exposure
• 2nd time the antigen stimulates Memory B cells and memory T cells to activate both humoral and cell-mediated responses.
• 2nd defense (about 3 days) where as 1st response is usually 7-10 days.
• Supressor T cells are thought to help turn off the immune response when antigens are gone.
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Antibodies
• A class of proteins referred to as the immunoglobulins (Ig) with 4 polypeptides (2 heavy chains and 2 light chains) held together by disulfide bridges to give them their quaternary structure
• Most of the antibody structure is identical for all antibodies with the “tips” variable that bind to the epitope (exposed) region on the antigen surface.
• Five types of immunoglobulins are divided by their constant regions IgM, IgG, IgA, IgD, and IgE.
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Immunoglobulin classes• IgM: large molecule that initiates response by
agglutinating (clumping up) the antigens• IgG: Most plentiful, triggers complement
proteins• IgA: Prevents attachment of antigens to
epithelial linings. Plentiful in mucus.• IgD: found on B-cells and probably initiate the
development of B-cells into plasma cells• IgE: small number, trigger the histamine release
of basophils and mast cells via receptor binding.
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Helper T-cells
• Helper T cells are stimulated by interleukin 1 of macrophages after engulfing antigens and presenting them.
• Helper T cells in turn stimulate the B cells of the humoral defense and the Cytotoxic T cells of the Cell mediated defense by releasing interleukin 2.
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