BSC 2086 1st Edition Lecture 15 Outline of Last Lecture I. Introduction to Lymphatic SystemII. Major Structures III. LymphocytesIV. Lymphoid System Components V. Lymphatic System and Body Defenses Outline of Current Lecture I. Nonspecific DefensesII. Specific Defenses III. Cells and Immunity IV. Immunity Disorders V. Effects of Aging on Immune System Current LectureI. Nonspecific Defenses a. *Continuation of “Lymphatic System and Body Defenses”b. Interferonsi. Cytokines (proteins) released by activated macrophages and lymphocytes1. Cytokines work as chemical messengers and are released by tissuecells2. Coordinate local activities3. Act as hormones to affect entire bodyii. Stimulate macrophage activity, NK cells and slows inflammationc. Complement i. 11 special complement (C) proteins found in plasma 1. Form complement system and complement antibody actionii. Complement activation1. Complements will work together in cascades2. Two pathways involved in activating the complement systema. Classical pathwayi. Fast methodii. Complement protein will bind with antibody molecule which is attached to antigen (bacterium)iii. Bound protein will act as enzyme and catalyze chain reactionb. Alternative pathwayi. Complement proteins interact with plasma ii. Results in attachment of activated complement protein onto bacterial cell wall 3. Both paths end in:a. Conversion of inactive complement protein C3 to active form C3b 4. Effects:a. Pore formation i. Destroy target plasma membranes1. Five complement proteins will join to form membrane attack complex (MAC)2. Causes cell to lyse b. Enhances phagocytosis i. Opsonization: complement coated items attract phagocytesc. Releases histamines i. Comes from mast cells and basophils ii. Increases local inflammation and the amount of local blood flow d. Inflammation i. Aka. inflammatory response ii. Local response iii. Triggered by any stimulus that kills cells or injures tissuesiv. Cardinal signs (quantitative – measurable) and symptoms (qualitative – you can feel them) 1. Swelling tumor2. Redness rubor 3. Heat calor 4. Pain dolorv. Effects:1. Temporary repair and barrier against pathogens 2. Stops spread of pathogens into the surrounding areas3. Mobilizing of local and specific defenses a. Facilitates repairs (regeneration)vi. Products: 1. Necrosis: destruction of local tissue in area of injury2. Pus: debris and necrotic tissue mixture3. Abscess: pus accumulation in an enclosed spacee. Feveri. Maintained body temperature above 37°C (99°F)ii. Pyrogens 1. Any material that causes a raise in body temperature by the hypothalamus a. Circulate pathogens, toxins, or antibody complexesiii. Endogenous pyrogens or interleukin-1 (IL-1)1. Cytokine released by active macrophages2. High temperature may stop some viruses/bacteria and increase body metabolism II. Specific Defensesa. Specific resistance (immunity)i. Responds to specific antigens with coordinated actions of the T cells and B cellsii. T cells 1. Cell mediated immunity2. Defend against abnormal cells and pathogens within cellsiii. B cells1. Antibody-mediated immunity2. Defend against antigens and pathogens within body fluids b. Forms of immunity i. Innate present at birthii. Adaptive found after birthiii. Active antibodies will develop after exposure to antigen 1. Naturally acquired: obtained from environmental exposure to pathogens 2. Artificially induced: obtained through vaccines containing pathogens a. Stimulates production of antibodies by immune systemiv. Passive antibodies transferred from a different source 1. Naturally acquired: antibodies acquired from the mother2. Artificially induced: by antibody injectionc. Four properties of immunityi. Specificity 1. Each T or B cells will only respond to a specific antigen and ignore any others2. Several thousand different types of lymphocytes exist, each with aspecific antigen receptor ii. Versatility 1. Body produces many types of lymphocytesa. Each will fight a different type of antigenb. The active lymphocyte will clone itself to fight a specific antigen iii. Memory1. Some active lymphocytes (memory cells):a. Stay in circulation and provide immunity against new exposure of same antigen iv. Tolerance1. Immune system will ignore normal antigens (self-antigens)d. Immune response i. Two main divisions1. Cell mediated immunity (T cells)2. Antibody-mediated immunity (B cells)III. Cells and Immunitya. Antigen Presentation i. T cells will ONLY recognize antigens that are bound to glycoproteins in plasma membranesii. Major Histocompatibility Complex (MHC) Proteins1. Human leukocyte antigens (HLAs) will differ among individuals 2. Membrane glycoproteins bind to antigens3. Types:a. Class I – found in the membranes of all nucleated cellsi. Pick up small peptides in cell cytoplasm and carry them to surface ii. T cells will ignore normal peptides iii. T cells will be activated when abnormal peptides or viral proteins are present and will destroy them b. Class II – found in membranes of antigen-presenting cells (APCs)i. Lymphocyte, phagocytic and non-phagocytic cells ii. Antigenic fragments 1. From the antigenic processing of pathogens a. Phagocytosis and breakdown of pathogens 2. Bind to class II proteins 3. Inserted into plasma membrane to stimulate T cells iii. Antigen-Presenting Cells (APCs)1. Responsible for activating T cells when foreign cells and proteins are present2. Class II MHC proteins only appear on the plasma membrane when cell is processing antigen 3. Phagocytic APCs a. Macrophages in connective tissuesb. Kupffer cells in the liverc. Microglia in the CNS4. Non phagocytic APCsa. Langerhans cells in the skinb. Dendritic cells in lymph nodes and spleen b. Antigen Recognitioni. Receptors found on inactive T cells can:1. Recognize either class I or class II MCH proteins or recognize specific antigenii. Binding will occur when MHC protein is attached to the specific antigen that the T cell is in charge of detecting c. CD Markersi. Membrane proteins found on T cells ii. Two types:1. CD8 Markers found on memory T cells, cytotoxic T cells and suppressor T cellsa. Respond to antigens on Class I MHC proteins 2. CD4 Markers found helper T cellsa. Respond to antigens on Class II MHC proteins d. Costimulationi. T cell must be costimulated in order for it to be activated1. Bind to either an infected cell or an APC (stimulating cell) at second sitea. This will confirm the first signal 2. Once activated the T
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