3.5 Hypersensitivity Flashcards
Which of the following is a description of a type I hypersensitivity reaction?
A. Ragweed antigen cross-links with IgE on the surface of mast cells, causing release of preformed mediators and resulting in symptoms of an allergic reaction
B. Anti-Fya from a pregnant woman crosses the placenta and attaches to the Fya antigenpositive RBCs of the fetus, destroying the RBCs
C. Immune complex deposition occurs on the glomerular basement membrane of the kidney, leading to renal failure
D. Exposure to poison ivy causes sensitized T cells to release lymphokines that cause a localized inflammatory reaction
A. Ragweed antigen cross-links with IgE on the surface of mast cells, causing release of preformed mediators and resulting in symptoms of an allergic reaction
Why is skin testing the most widely used method to test for a type I hypersensitivity reaction?
A. It causes less trauma and is more cost effective than other methods
B. It has greater sensitivity than in vitro measurements
C. It is more likely to be positive for IgE-specific allergens compared with other methods
D. It may be used to predict the development of further allergen sensitivity
B. It has greater sensitivity than in vitro measurements
Which in vitro test measures IgE levels against a specific allergen?
A. Histamine release assay
B. Radioimmunosorbent test (RIST)
C. Fluorescent allergosorbent test (FAST)
D. Precipitin radioimmunosorbent test (PRIST)
C. Fluorescent allergosorbent test (FAST)
A patient who is blood group O is accidentally transfused with group A blood and develops a reaction during the transfusion. What antibody is involved in this type II reaction?
A. IgM
B. IgE
C. IgG and IgE
D. IgG
A. IgM
Which test would measure the coating of RBCs by antibody as occurs in hemolytic transfusion reactions?
A. Indirect antiglobulin test (IAT)
B. Direct antiglobulin test (DAT)
C. ELISA
D. Hemagglutination
B. Direct antiglobulin test (DAT)
Which test detects antibodies that have attached to tissues, resulting in a type-II cytotoxic reaction?
A. Indirect immunofluorescence
B. Direct immunofluorescence (DIF)
C. Immunofixation electrophoresis (IFE)
D. Hemagglutination
B. Direct immunofluorescence (DIF)
The direct IFA detects the presence of antibody that may cause a type II cytotoxic reaction. For example, renal biopsies from patients with Goodpasture syndrome exhibit a smooth pattern of fluorescence along the basement membrane after reaction with fluorescein isothiocyanate (FITC)-conjugated anti-Ig. The reaction detects antibodies against the basement membrane of the glomeruli.
Which of the following conditions will most likely result in a false-negative DAT test?
A. Insufficient washing of RBCs
B. Use of heavy chain–specific polyclonal anti-human Ig
C. Use of excessive centrifugal force
D. Use of a sample obtained by finger puncture
A. Insufficient washing of RBCs
Which of the following tests will detect circulating immune complexes in the serum of some patients with systemic autoimmune diseases, such as RA?
A. Direct IFA
B. Enzyme immunoassay (EIA)
C. Assay of cryoglobulins
D. IAT
C. Assay of cryoglobulins
Most autoimmune diseases involve the formation of antigen-antibody complexes that deposit in tissues, causing local inflammation and necrosis induced by complement activation, phagocytosis, white blood cell (WBC) infiltration, lysosomal damage. Some patients make monoclonal or polyclonal antibodies with RF activity that bind to serum Igs, forming aggregates that are insoluble at 4C. These circulating immmune complexes are detected by allowing a blood sample to clot at 37C, transferring the serum to a sedimentation rate tube, and then incubating the serum at 4C for 3 days.
What immune elements are involved in a positive skin test for tuberculosis?
A. IgE antibodies
B. T cells and macrophages
C. NK cells and IgG antibody
D. B cells and IgM antibody
B. T cells and macrophages
A patient receives a transfusion of packed RBCs and fresh frozen plasma (FFP) and develops an anaphylactic, nonhemolytic reaction. She reports receiving a transfusion 20 years earlier. She had no reaction to the previous transfusion, but she did feel “poorly” a few weeks later. Which of the following transfused substances most likely elicited the reaction?
A. IgA
B. Group A antigen
C. Rho (D) antigen
D. An antigen belonging to the Duffy system
A. IgA
A patient deficient in the C3 complement component would be expected to mount a normal:
A. Type I and IV hypersensitivity response
B. Type II and IV hypersensitivity response
C. Type I and III hypersensitivity response
D. Type II and III hypersensitivity response
A. Type I and IV hypersensitivity response
