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Phys Exam 3: Ch 34
Immunity and Allergy
| Question | Answer |
|---|---|
| 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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