Hypersensitivity Flashcards
What are the characteristics of the infiltrate in a delayed hypersensitivity reaction?
An infiltrate composed of helper T cells and macrophages.
A child disturbs a wasp’s nest, is stung repeatedly, and goes into shock within minutes, manifesting as respiratory failure and vascular collapse. What is the most likely cause of these symptoms?
Systemic anaphylaxis
A wheal and flare reaction is typical of which type of hypersensitivity reaction?
Type 1
A 77-year old man with enterococcal endocarditis needs to be treated with penicillin G but has a history of severe penicillin reactions. He was therefore tested using a dermal injection of penicilloyl-polylysine, a molecular mimic of penicillin, as a test antigen. How is the test antigen most likely to interact with the immune system upon injection?
The antigen cross-links IgE on the mast cells and causes release of histamine
A kidney biopsy taken from a patient with acute glomerulonephritis is stained with fluorescently labelled anti-human IgG antibody. What is likely to be observed in the biopsy?
Patchy, irregular fluorescence of the glomerular basement membrane.
Drug X is a small molecule. It is commonly taken as a pain reliever. Some individuals who take it repeatedly develop an adverse reaction that results in depletion of red blood cells. What type of molecule is drug X likely to be?
A hapten
A 40-year old woman has a history of chronic inflammation of the small joints of the hands bilaterally. You suspect rheumatoid arthritis. How would you accurately describe the pathogenesis of the disease?
It is caused by antibody against IgG forming immune complexes within the joints
How would you accurately describe the relationship between anaphylactic and immune complex hypersensitivities?
Less antigen is typically needed to trigger an anaphylactic reaction than an immune complex reaction
A patient with severe asthma, who has disease exacerbations associated with rapid contraction of the airways, gets no relief from anti-histamines. A skin prick test reveals they are allergic to the common aero-allergen house dust mite. Given this, which molecule(s) could likely cause the symptoms?
Leukotrienes
CD4+ versus CD8+ T cell responses?
Activation of macrophages, B cells and other cells
vs
Killing of infected cells and macrophage activation
3 stages of Type I mechanism?
- Activation of type 2 helpter CD4 T cells and B cell helper follicular CD4 T cells to produce type 2 cytokines IL-4 and IL-13
- These cytokines promote B cells to produce antigen specific IgE
- IgE rapidly binds to mast cells and basophils via the Fc epsilon receptor 1 to cause crosslinking and degranulation
What is Type II hypersensitivity?
Involves destruction of cells by IgG or IgM antibodies, either by exposure to foreign antigen or aberrant response to self-antigen
3 antibody responses to Type II hypersensitivity
- Blocking receptor activity
- Antibody dependent cell-mediated toxicitiy (ADCC)- formation of antibody-antigen complexes on surfaces of cell Fc receptors for granulocytes and NK cells
- Classical activation of complement cascade, e.g MACs
What is Type III hypersensitivity?
Immune complex driven disease- non-cell bound antigen-antibody complexes not cleared by the immune system. E.g found in blood vessels
E.g glomerulonephritis, rheumatoid arthritis and lupus
What is Type IV hypersensitivity?
T cell mediated hypersensitivity, is delayed. Causes swelling and thick lesion
E.g contact dermititis caused by poison ivy upon subsequent re-exposure
