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46 Cards in this Set
- Front
- Back
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What is type I hypersensitivity?
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An anaphylactic and atopic response mediated by IgE cross-linking antigens to host cells
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What is type II hypersensitivity?
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A cytotoxic response mediated by antigen binding with IgG and IgM on host cells
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What is type III hypersensitivity?
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An immune response mediated by antibodies binding to host tissue iwth ensuing inflammation
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What is type IV hypersensitivity?
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A delayed, cell-mediated response mediated
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What is a type 1 hypersensitivity reaction?
What are two examples |
An anaphylactic and atopic response mediated by IgE cross-linking antigens to host cells
Systemic anaphylactic reaction Atopic reaction |
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What is systemic anaphylaxis?
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A life-threatening IgE mediated hypersensitivity, characterized by severe hypotension, bronchoconstriction, and massive release of mast cell and basophil mediators
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What are three common causes of systemic anaphylaxis?
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Drugs
Insect venom Food |
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What is an atopic reaction?
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A non-life threatening IgE-mediated hypersensitivity, characterized by a localized inflammatory process
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What is a common example of an atopic reaction
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Atopic dermatitis seen in athmatics (eczema)
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What host cell receptors does IgE target?
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Fc receptors of mast cells and basophils
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What common factor do mast cells and basophils release?
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histamine
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What are five other substances released by mast cells?
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1) Platelet-activating factor (PAF)
2) Thromboxanes 3) Prostaglandins 4) Chemotactic fators for eosinophils and neutrophils 5) Slow-reacting substance of anaphylaxis (SRS-A) |
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What is the difference between anaphylaxis and anaphylactoid reactions?
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Anaphylactoid reactions do not involve IgE
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What is a type II hypersensitivity reaction?
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A cytotoxic response mediated by antigens binding with IgG and IgM on host cells
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What are two mechanisms for Type II hypersensitivity reactions?
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1) Lysis of cells because of either complement activation (direct) or opsonization (indirect)
2) Antibody-dependent cell-mediated toxicity (ADCC) predominately by natural killer (NK) cells |
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What are three common tagets of cytotoxic hypersensitivity?
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1) Erythrocyte membrane (transfusion reaction)
2) Antigens of BM (goodpastures) 3) Acetylcholine (ACh) receptors |
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What are three clinical manifestations of type II hypersensitivity against the erythrocyte membrane?
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1) ABO incompatibility (transfusion reactions)
2) Rh incompatibility (erythroblastosis fetalis) 3) Drug-induced hemolytic anemia |
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What class of antibody is associated with ABO incompatibility?
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IgM
IgM is primarily found in the serum |
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What class of antibody is associated with erythroblastosis fetalis?
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IgG
IgG is the only immunoglobulin that can cross the placenta Maternal antibody that is formed to previous exposure to Rh antigen, which subsequently crosses the placenta in a pregnancy |
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What two conditions predispose the mother to develop this particular IgG?
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1) Second or subsequent Rh+ fetus born to an Rh- mother
2) Exposure to the Rh antigen in a blood transfusion |
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How does penicillin cause a type II hypersensitivity drug-induced hemolytic anemia?
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Covalent linkage of penicillin to erythrocyte membrane proteins
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x
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x
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What is another mechanism by which penicillin can cause a hypersensitivity reaction?
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By a type III hypersensitivity
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What are two autoimmune clinical manifestations of type II hypersensitivity?
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Goodpastures disease
Myasthenia gravis |
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What is goodpastures disease?
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Disease characterized by an immune response against the lung and kidney parenchyma basement membranes.
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What is myasthenia gravis?
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Disease causing fatigable skeletal muscular weakness because of autoantibodies to ACh receptor
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Which muscles are most seriously affected in myasthenia gravis?
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Diaphragm and muscles innervated by cranial nerves.
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What is a type III hypersensitivity reaction?
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An immune response mediated by antibodies binding to host tissue with ensuing inflammation.
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What initiates a type III hypersensitivity reaction?
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Insoluble antigen-antibody complexes
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What are two mechanisms of type III hypersensitivity?
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1) Complement activation with neutrophil diapedesis
2) Factor XII (Hageman factor) activation |
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What three coagulation cascade factors are activated in type III hypersensitivity via Hageman factor?
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Kinin
Fibrin Plasmin |
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What are general common presentations of immune complex-mediated reactions?
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Rash
Fever Lymphadenopathy Arthralgia |
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What are six clinical manifestations associated with type III hypersensitivity?
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1) Serum sickness
2) Arthus reaction 3) Polyarteritis nodosa (PAN) 4) Poststreptococcal glomerular nephritis 5) Systemic lupus erythematosus 6) Rheumatoid arthritis |
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What is serum sickness?
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Immune complex vasculitis 7-10 days following drug or allergen exposure
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What symptoms are seen in serum sickness?
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Fever
Arthralgia/Arthritis Acute Glomerular nephritis Vasculitis Urticaria Purpura Lymphadenopathy |
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Is the severity of serum sickness dose-dependent?
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YES
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What are two common causes of serum sickness?
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Drugs (penicillin and streptokinase)
Antibody therapy (monoclonal or polyclonal) |
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What is another mechanism by which penicillin can cause a hypersensitivity reaction?
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Preformed antibodies activate complement to subcutaneously infected antigen causing inflammatory cell attraction and increased vascular permeability resulting in edema
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What is an example of an Arthus reaction?
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Immune complex hypersensitivity reaction to tetanus toxoid in an individual previously immunized with the tetanus vaccine
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What type is a type IV hypersensitivity reaction?
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A delayed, cell-mediated response mediated by T lymphocytes that encounter antigens and release inflammatory components
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What type of cell initiates the host response in type IV?
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CD4+ T-helper cells
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What are three steps of a type IV reaction response?
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1) Antigen processing in macrophage
2) T-helper cells stimulated by macrophage antigen-major histocompatibility complex class II complex and interleukin-1 3) Activation of other T-helper cells and macrophages |
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What are three examples of type IV reactions?
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1) Tuberculin skin test (purified)
2) Contact dermatitis (poison ivy) 3) Transplant reaction |
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How si the PPD response evaluated?
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Diameter of induration (swelling NOT reddening)
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When is the PPD response evaluated?
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48-72 hours after injection
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Is a positive PPD diagnostic of active disease?
What does it indicate? |
NO
PPD tests only indicates that an infection has occurred at some point or that the person has received bacillus Calmette-Guerin vaccine |
