Presentation on theme: "Chapter 16 Disorders of the Immune Response"— Presentation transcript:
1Chapter 16 Disorders of the Immune Response Essentials of PathophysiologyChapter 16 Disorders of the Immune Response
2PRE LECTURE QUIZ (True/false) Allergic rhinitis is a systemic, life-threatening hypersensitivity reaction characterized by widespread vasodilation that leads to severe hypotension, airway constriction that causes difficulty breathing, and vascular permeability that causes swelling and obstruction of the upper airway.Virtually any food can produce an allergic reaction.In host-versus-graft disease, the immune cells of the transplant recipient attack the donor cells of the transplanted organSevere combined immunodeficiency is a disorder that results from the loss of B-cell function, while all other immune function remains normal.The HIV-infected person can transmit the virus only when symptoms are present and the antibody test is positive.
3PRE LECTURE QUIZAutoimmuneIOpportunisticSelftuberculinType __________ hypersensitivity responses result from immune responses to exogenous and endogenous antigens that produce inflammation and cause tissue damage.The _______________ test, a test in which purified protein derivative is injected under the skin, is an example of delayed-type hypersensitivity.Rheumatoid arthritis, insulin-dependent diabetes mellitus, ulcerative colitis, and myasthenia gravis are all examples of probable ___________________ disease.The HIV-infected person is at risk for many ___________ infections, potentially affecting the respiratory tract, the gastrointestinal tract, and the nervous system._____________ tolerance refers to the inability to mount an immune response against a person’s own antigens.
4HypersensitivityExcessive or inappropriate activation of the immune responseThe body is damaged by the immune response, rather than by the antigen (often called allergen)Discussion:How many different allergies do the members of this class have?What are their common signs and symptoms?Can the general process of inflammation explain these signs and symptoms?
5Type I Hypersensitivity Commonly called “allergic reactions”Systemic or anaphylactic reactionsLocal or atopic reactions (genetic)Rhinitis (hay fever)Food allergiesBronchial asthmaHivesAtopic dermatitis (inherited)
6Mechanism of Type I Hypersensitivity Mast cellMechanism of Type I HypersensitivityAllergenAllergenattachesto IgEIgE attaches to mast cellSensitized Mast cellMast cell degranulates
7Type I Allergies Are Mediated by IgE What cells must be involved in this process:On the first exposure to the allergen?On repeated exposure?When the allergen binds to IgE?What inflammatory mediators are involved? How?
8QuestionTrue or False. When mast cells degranulate, histamine is released.
9AnswerTrue Rationale: Histamine is one of the first chemical mediators released during the inflammatory response as a result of mast cell degranulation. Mast-cell stabilizers (used to treat asthma) prevent the histamine from being released; antihistamines (used to treat allergies) compete with histamine for receptor sites, lessening the inflammatory response.
10AnaphylaxisSystemic response to the inflammatory mediators released in type I hypersensitivityHistamine, acetylcholine, kinins, leukotrienes, and prostaglandins all cause vasodilationWhat will happen when arterioles vasodilate throughout the body?Acetylcholine, kinins, leukotrienes, and prostaglandins all can cause bronchoconstrictionWhat will happen when the bronchioles constrict?
11ScenarioA woman had an anaphylactic reaction and you are trying to explain the mechanism to her husband; he says he can see what you mean, but it does not make sense because what his wife experienced was different.She said her heart was pounding and she was terrified.Her eyes were dilated.She was shaking.Question:How could anaphylaxis cause these signs and symptoms?
12Type II Hypersensitivity CytotoxicIgG or IgM attack antigens on cell surfacesUsually involves antigens on red or white blood cellsTransfusion reactionsRh diseaseDrug reactions
13Mechanism of Type II Hypersensitivity Example incompatable blood transfusionImmunoglobulinsImmunoglobulins attach to antigensAntigens introducedComplement activatedDirectlycauses cell lysisCell lysisWBCs attracted to eat cell
14ScenarioA woman is Rh negative and her husband is Rh positive.She is pregnant with their first child and the doctor has prescribed RhoGAM, but the woman is confused about this.She says she does not want to take any drugs while she is pregnant—and besides, the doctor told her that her first child was not at much risk for Rh disease.Question:Why can’t she wait to take RhoGAM until she gets pregnant again and really needs it?
15RHOgam a solution of IgG anti-Rh+ antibodies bind to, and lead to the destruction of, Rh+ red blood cells that have passed from the fetal circulation to the maternal circulation.prevents sensitization in a Rh negative mother to Rh+ antigens,Sensitization can cause hemolytic disease in the current or in subsequent pregnancies.
16QuestionWhy is type O blood considered the universal donor?It has both A and B antigens on the RBC.It has neither A nor B antigens on the RBC.It has no antibodies in the plasma.It has A and B antibodies in the plasma.
17AnswerIt has neither A nor B antigens on the RBC.Rationale: Antigens are the components that elicit an immune response (type II hypersensitivity reaction). Type O blood has no antigens on the RBC, so anyone can receive it because there is nothing to stimulate production of antibodies against it. The fact that type O blood has both A and B antibodies has nothing to do with creating the antigen- antibody response.
18Type III Hypersensitivity Free-floating antigen + antibody circulating immune complex in the circulatory systemAutoimmune vasculitisGlomerulonephritisSerum sicknessArthus reaction
19Mechanism of Type III Hypersensitivity Immune complexes deposit on walls of blood vessels and activate complementBlood vessels are damagedImmunoglobulinsAntigensImmune complexes
20QuestionTrue or False. Administration of certain antibiotics may result in type III hypersensitivity reaction.
21AnswerTrue Rationale: A side effect associated with antibiotic administration (especially penicillin) is serum sickness, which may cause a type III hypersensitivity reaction.
22Type IV Hypersensitivity (Cellular immunity) Cell-mediated: sensitized T cells attack antigenDirect cell-mediated cytotoxicityViral reactionsDelayed-type hypersensitivityTuberculin testAllergic contact dermatitisHypersensitivity pneumonitis
23Mechanisms of Type IV Hypersensitivity TH1 cellAntigenSensitized TH1 cellDelayed-type hypersensitivity: TH1 cell secretes inflammatory mediatorsActivated Cytotoxic T cellDirect cell-mediated cytotoxicity: Cytotoxic T cells kill tissue cells
24Mechanisms of Type IV Hypersensitivity An antigen enters the systemThe antigen is taken up, processed, and presented on the surface of APC and local cellsAPC cells present epitope to T4 helper cellsT4 cells stimulate T8 cytotoxic cells to destroy local cells that have taken up the antigen.T4 cells release cytokines that initiated an inflamatory responseExample: TB tine testT4
25Autoimmune Diseases Immune system attacks self-antigens Normally, self-reactive immune cells are killed in the lymphoid organs or suppressed by regulatory T cellsIn autoimmunity, this self-tolerance breaks downImmune system destroys body tissuesAntitissue antibodies appear in blood (e.g., antithyroid antibodies)
26Transplant Rejection Host-versus-graft disease (HVGD) Hyperacute Circulating antibodies react with graftAcuteExposure to transplant causes activation of immune system, especially T cellsChronicBlood vessels in transplant gradually damaged
27Graft-versus-host Disease Transplanted immune cells attack hostA recent study suggested that men who get bone marrow transplants from women might be more prone to GVHD than men who get bone marrow transplants from other menIt also suggested that the more children a woman has had, the more likely her bone marrow will cause GVHDDiscussion:Why might this be the case?
28QuestionTrue or False. Patients who suffer from autoimmune disease have hypoactive immune systems.
29AnswerFalse Rationale: In autoimmune diseases, the immune system is hyperactive—it attacks self-antigens and destroys its own body tissues.
31Human Immunodeficiency Virus Transmitted by body fluidsSexual contactBreast milkBlood-to-blood contactContaminated needlesTransfusionsDuring pregnancy or birth
32Which of your body cells have CD4 proteins and CD4 receptors? What does reverse transcriptase do?HIV Infects a CellBinds to CD4 protein receptorBindUncoatIntegrate
33The Infected Cell Produces New HIV Polyprotein broken into subunits by proteaseHIV may lie dormant in the genome for many years before it is activated to produce viral proteinsViral proteins are produced in a long string called a polyproteinTranscriptionProtein subunits are assembled into new virus particlesExit
34QuestionOne AIDS drug is a fusion inhibitor (Fuzeon)—the drug prevents fusion of HIV to the CD4 receptor. In the previous slides’ illustrations, which step in the infection process is targeted by a fusion inhibitor?1368
35Answer1 Rationale: In the illustration, step #1 marks the point of attachment between HIV and the CD4 receptor site on the T lymphocyte.
36Course of HIV Infection Primary infection phaseSigns of systemic infectionSeroconversion: immune system responds and antibodies against HIV appear (1–6 months)Latent periodVirus is replicating, TH cell count gradually fallsMay last 10–11 years or longerOvert AIDSTH cell count <200 cells/mL or AIDS-defining illness
38Scenario A man was diagnosed as HIV-positive. He says this is nonsense because the test does not measure whether he is sick or notIn fact, it means “his immune system is working”Question:Is he right?