Chapter 51- Immune System
Chapter 51- Immune System BIOL 1006
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This 5 page Class Notes was uploaded by Gina Nam on Saturday March 26, 2016. The Class Notes belongs to BIOL 1006 at Virginia Polytechnic Institute and State University taught by Dr. Denbow in Spring 2016. Since its upload, it has received 16 views. For similar materials see General Biology in Biology at Virginia Polytechnic Institute and State University.
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Date Created: 03/26/16
Chapter 51: Immune System INNATE IMMUNITY Vertebrates have3 levels of defense o Integumentary System o Nonspecific (innate) Immune System o Specific Immune System Skin o Serves as a barrier to infections Use of chemicals such as sweat and oil to inhibit growth of bacteria o Contains flora nonpathogenic bacteria or fungi adapted to the skin conditions o Digestive, respiratory, and urogenital are all lined with epithelial cells Digestive microbes are killed by the acidity and the digestive enzymes Respiratory cilia; it sweeps the mucus to the glottis which leads to the digestive tract Urogenital acidity of urine keeps pathogens away Innate Immunity recognizes characteristic pathogen molecules o Receptor proteins that identify invading pathogens and induce a response and lead to signal transduction pathway Pattern recognition receptors (PRR) Tolllike receptors Innate Immunity leads to diverse responses to a pathogen o Nonspecific defensive molecules Defensins Cathelicidin Interferon o Inflammatory response o Activation of complement pathway Phagocytic Cells o Macrophages Ingests microorganisms/ bacteria througphagocytosis Mature from monocytes Monocytes found in blood enter the connective and to the infected area; here, they mature to macrophages o Neutrophils Kills microorganisms/bacteria in the same matter as macrophages Difference: produce a greater range of reactive oxygen radicals o Natural killer cells Induce apoptosis (cell death) infected cells rather than invading cells Inflammatory response o Involves several body systems o Histamines and prostaglandin are released as a chemical alarm Cause vasodilation increase in blood flow at the site Increase permeability of capillaries o Release of acutephase proteins Bind to a variety of microorganisms and promote their ingestion by the neutrophils and macrophages Complement System o A group of approximately 30 different proteins circulating in the blood plasma o Form a membrane attack complex (MAC) Inserts itself onto the plasma membrane, form a pore, allow extracellular fluid to enter, and cell bursts ADAPTIVE IMMUNITY Antigens stimulate a specific immune response o Antigenic determinants, or epitomes areas that are recognized as foreign to the body Hematopoiesis o Differentiation process of the hematopoietic stem cells Cells found in the blood o Give rise to lymphoid and myeloid progenitors Lymphoid gives natural killer cells Myeloid gives all other white blood cells Lymphocytes o Leukocytes derive from lymphoid progenitor o Rare that two lymphocytes have identical specificities o Adaptive immunity is characterized Specificity Diversity Selfnonself recognition Memory o Naïve lymphocytes lymphocyte that has never encountered an antigen once bound to the antigen goes through a process calclone selection and multiplies, and become memory cells o B cells Respond to antigens by secreting antibodies or immunoglobulins (Ig) Calledhumoral immunity o T cells Regulate immune responses or directly attacks the cell with the specific antigen Participate icellmediated immunity Adaptive Immunity can be active or passive o Active gaining immunity after direct exposure or immunized with portions of the pathogen (vaccinations) o Passive transfer of antibodies to gain immunity (mothers milk) Immune System supported by two classes of organs o Primary lymphoid organ Bone marrow and thymus o Secondary lymphoid organ Lymph nodes, spleen, and mucosaassociated lymphoid tissue (MALT) Primary Lymphoid Organ o Bone marrow Site for B cell maturation Any cell that are likely to bind to selfantigens undergo apoptosis before releasing the mature cells into the blood stream Recognize epitomes that may or may not be a protein o Thymus Site for T cell maturation Recognizes epitopes only if it is combined with major histocompatibility complex (MHC) peptides Secondary Lymphoid Organ o Locations of lymphoid organs promote the filtering of antigens that enter any part of the body E.g. GI tract is full of bacteria which can prevent antigen growth o Naïve B and T lymphocytes become activated in the lymph nodes CELLMEDIATED IMMUNITY T cells have two different types o Cytotoxic T cells o Helper T Cells Both are distinguished by cell surface markers Two classes of MHC proteins o MHC class 1 proteins : present on every nucleated cell T cells respond to class 1 Dendritic cells ingests the virus or tumor cell and places the peptides on the MHC class 1 protein for the T cell to respond to T cell undergoes clonal expansion producing both memory cell and activated cells o Activated T cells circulates around and destroys target cells through apoptosis o MHC class 2 proteins : found only on antigenpresenting cells Helper T cells respond to class 2 Secrete cytokines that promotes activation or differentiation of immune system cells HUMMORAL IMMUNITY AND ANTIBODY PRODUCTION Immunoglobulin structure o Light chains two short polypeptides o Heavy chains two longer polypeptides o Held together by disulfide bond o Yshaped molecule o Each chain has a variable and a constant region Variable region Amino acid sequence that differ from other immunoglobulin Form to make the antigenbinding site o Determines the specificity for an antigen epitope Variable region is produced by encoding several DNA strands together DNA rearrangement o DNA rearrangement occurs in mature B cells in the bone marrow Formation from V, D, and J clusters (DNA segments) o RNA transcription to mRNA which is translated to either a heavy or light chain immunoglobulin polypeptide o Creates diverse antibody specificity Constant region Amino acid sequence that relatively stays constant Heavychain constant region determines class of immunoglobulin o 5 different classes Also determines the function of the Fc region Primary and Secondary Responses o Primary Immune Response Antigens come across naïve lymphocytes Only a few B and T cells mount to create a response o Secondary Immune Response Memory cells encounters the same antigens making the response more quickly and more effective AUTOIMMUNITY AND HYPERSENSITIVETY Immunological tolerance o Immune system does not effect on its own tissueacceptance of self cells Autoimmune diseases is the failure of immunological tolerance Antibodies in Medical Treatment o Blood types Determined by the antigens found on the surface of red blood cells A, B, AB, and O are all different antigens Transfusion: People with type A blood can only donate to other Type A patients because B, AB and O blood produce antiA antigens o Monoclonal antibodies Specific to only one epitome
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