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Phys Exam 3: Ch 34

Immunity and Allergy

Compare (generally) innate immunity and acquired immunity Innate: defenses you are born with; Acquired: develop over time in response to antigens (infections)
What is the basis of the cell-mediated immune system? WBC-based, based on activation of T-cells and other immune cells
What is the role of the complement system? Blood-born protein system that marks cells for phagocytosis
Describe some of the ways the innate immune system works 1. Resistance of the skin to bacterial penetration; 2. Enzymes & acid in epithelial secretions; 3. Phagocytosis via WBCs; 4. Proteins & enzymes in blood that specifically attack bacteria; 5. Complement system; 6. Natural Killer lymphocytes
Describe the complement system Blood-born protein system that marks cells/pathogens for phagocytosis; we have the genes, they develop
Describe how natural killer lymphocytes work They recognize non-self cells by the ABSENCE of MHC-1 protein, and they bind to anything that has ABs attached
What is an AB? Large proteins w/a binding site specific for a particular antigen
What is an antigen? Fragment of a non-self macromolecule, usually a protein or glycoprotein
Review the types of WBCs that are non-phagocytic, and how they work since they are non-phagocytic Lymphocytes (B- & T-cells), ~20-50% of WBCs, secrete peptides/ABs
Describe a B lymphocyte/B-cell cells that secrete ABs after binding a specific antigen - only produce 1 specific AB, and all ABs produced by that single B-cell are identical
Describe a T lymphocyte/T-cell Cell that secretes cytokines after binding a specific antigen - "send messages" to activate B-cells
Describe the action of B-cells in response to specific antigens Develop into: 1. plasma cells - make ABs against a specific antigen; 2. Memory cells - dormant until the next exposure to that same antigen (THIS IS THE BASIS OF IMMUNITY)
What is the basis of immunity (i.e. how do vaccinations work)? B-cells make ABs against a specific antigen, and some become dormant (memory cells) until the next exposure to the same antigen
Describe the action of T-cells in response to specific antigens Are activated to: 1. Stimulate rapid division of B-cells; 2. Stimulate production of cytotoxic T-cells
What is the fxn of T-cells within a lymph node after binding their specific antigen? Direct responses of other lymphocytes: activate more T- & B-cells w/antigens bound; B-cells clone in response to activated T-cells
What is the fxn of B-cells within a lymph node after binding their specific antigen? Produce ABs
What is the basic structure of an antibody? 2 heavy chains (constant portion), 2 light chains (variable portion), 2 antigen-binding sites located in the variable portion
Why does an antibody have a hinge between the heavy and light chains? To facilitate binding 2 separate antigens
What are the 4 actions of ABs? 1.Neutralization: cover toxic or active site of antigen; 2.Precipitation: form insoluble particle w/antigen; 3.Agglutination: clump bacteria together, immobilize them; 4.Opsonization: mark non-self cell for destruction by cytotoxic T-cells (complement P)
List the 4 types of ABs IgM, IgG, IgA, IgE
Describe IgM ABs "First responders" - first ABs formed in an infection; pentamers
Describe IgG ABs Formed later in an infection, also formed by memory cells; most abundant type of AB in BLOOD
Describe IgA ABs Found in mucous secretions of GI tract; dimers; most abundant type in the BODY
Describe IgE ABs these induce degranulation of mast cells and basophils
Describe the role of T-cells in cell-mediated immunity Regulate the proliferation & activity of other immune cells: cause rapid division of B-cells, activate macrophages & PMNs
What are the 2 primary types of T-cells? 1. Helper T-cells - T4 cells - CD4 T-helper cells; 2. Cytotoxic T-cells - T8 cells - CD8 T-helper cells
Where do T-cells develop? Thymus
Describe the maturation of T-cells in the thymus 1. Immature T-cells divide in the thymus, extreme diversity; 2. Developing T-cells are exposed to self-antigens; 3. T-cells that bind self-antigens undergo apoptosis; 4. The only T-cells released from the thymus are those that bind to non-self antigens
What do cytotoxic T-cells (CD8 cells) do? Lyse MHC class-I antigen-presenting cells
What do helper T-cells (CD4 cells) do? Bind to MHC class-II antigen-presenting cells, then secrete cytokines that activate other immune cells
What are Major Histocomplatibility (MHC) proteins? Large glycoproteins found on the surface of body cells that bind fragments of antigens degraded inside the cell
Where do you find MHC Class I proteins, and what do they do? On ALL nucleated cells - allow cytotoxic (CD8) cells to bind to cells that have antigen on their surface (infected or non-self cells)
Where do you find MHC Class II proteins, and what do they do? ONLY on antigen-presenting cells (APCs) - dendritic cells, macrophages, B-cells; allow helper (CD4) cells to bind to and be activated by an antigen on the surface of the APC
What is the role of antigen-presenting cells (APCs)? 1. break down a non-self molecule into small fragments (epitopes) and incorporate these fragments onto their cell membrane; 2. The APC then "presents" the fragment to the active site of T-cells
What types of cells are considered APCs? Dendritic cells, macrophages, B-cells
Describe the activation of a T-cell An APC presents an MHC-bound antigen to the TCR (T-cell receptor); the T-cell receptor recognizes the antigen. Cell-cell adhesion proteins hold the 2 cells together
What are the 3 fxns of T-helper (CD4) cells? 1. Stimulation of growth & differentiation of: B-cells into plasma cells & memory cells, cytotoxic (CD8) T-cells and suppressor T-cells; 2. Activation of macrophages; 3. Stimulation of other helper (CD4) T-cells
What to CD4 cells activate? macrophages, other CD4 cells
What do B-cells differentiate into, and in response to what signal? Signal from a CD4 cell, plasma cells & memory cells
What non-B-cells do CD4 cells stimulate the growth and differentiation of? CD8 T-cells and suppressor T-cells
Describe the the action of the CD8 cells Receptors on the CD8 (cytotoxic) T-cell surface bind antigen on target cell (cell to be attacked), then secrete perforins that will form holes in the target cell membrane
What is the fxn of the complement system? A group of blood proteins that mark bacteria for lysis, phagocytosis/opsonization...
In the complement system, what does activates the C1 enzyme? the Antigen-AB complex
In the complement system, what does the C1 enzyme do? Cleaves C4 & C2 into C4b2a and C4a
In the complement system, what does the C4b2a enzyme do? cleaves C3 into C3b and C3a
In the complement system, what does the C3b enzyme do? inserts into the bacteria and activates phagocytosis (this is opsonization); also initiates formation of a protein that lyses bacteria
What is an allergy? Some antigens induce formation of IgE ABs --> IgE ABs bind to Mast cells --> When next exposed to that antigen, the antigen binds to the IgE molecules --> triggers histamine release from Mast cell --> induces inflammatory response
What is an allergen, and what are some of its characteristics? Antigens that induce IgE; most allergens and most parasites have proteases on their surface
What are some sx of allergies? Nasal cavity: inflammatory response is hay fever w/post-nasal drip & sneezing; Skin: hives & itching; Bloodstream: anaphylactic shock and whole body vasodilation
Created by: hclark86



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