L16: Hypersensitivity Flashcards
What antibody does Type I hypersensitivity involve and what does it trigger?
IgE-dependent triggering of mast cells (commonly referred to as allergy)
Which antibody is involved in Type II hypersensitivity reactions?
IgG antibody that is reactive with cell-surface or matrix antigens
What type of cell can induce B cell class switching from IgM to IgE?
TH2 CD4 cells.. Allergens will stimulate TH2 cells to drive an IgE response.
Allergens are presented to the immune system at low doses. What will any antigen at low doses with low binding affinity stimulate TH0 cells to differentiate into?
TH2 cells for extracellular infections.
What will IL-4, IL-5, and IL-13 do to to B lymphocytes?
stimulate class switching from IgM to IgE
What do TH2 cells do after being activated?
secrete IL-4, IL-5, and IL-13.
Upregulate surface expression of CD40 and CD23 to bind to CD40 and CR2 on B cells.
What is atopy?
predisposed state to produce IgE responses to common environmental antigens. They have higher levels of soluble IgE and more circulating eosinophils that non-atopic individuals
What are IL-3,4,5,9,13 and GM-CSF involved with?
isotype switching, eosinophil survival and mast cell proliferation
what is a wheal and flare?
immediate reaction where mas cell-degranulation in the skin releases histamine and other mediators to cause local edema which forms a wheal, and inrecreased blood flow causes redness (flare)
What is the late phase reaction of type 1 hypersensitivity?
6-8 hours post injection, a second reaction occurs at the site. consists of more widespread swelling and is mediated by leukotrienes, chemokines and cytokines prodcued by mast cells following IgE-mediated activation
What is systemic anaphylaxis?
wide-spread activation of mast cell degranulation causing both an increase in vascular permeability and widespread constriction of smooth muscle.
What are anaphalactoid reactions?
reactions that resemble anaphylactic reactions, but do not involve interaction between allergen and IgE
How does epinephrine help anaphylactic reactions?
stimulates reformation of tight junctions betwen endothelial cells, reducing permeability of blood vessels and diminishing swelling, raising blood pressure and relaxing constricted bronchial smooth muscle as well as stimulating the the heart.
What is allergic rhinitis?
hay fever. mild allergic response characterized by violent bursts of sneezing and runny nose in response to inhaled allergens.
What is allergic conjunctivitis?
inflammation of membrane overlaying eyelid
What is allergic asthma?
reaction to inhaled allergens causes chronic breathing difficulties. Can be fatal by trapping of air in lungs. Can be exacerbated by immune responses to bacterial or viarl infection of the respiratory tract (especially infections that illicit TH2 response)
What type of hypersensitivity if chronic asthma?
***TYPE IV.
because it is exacerbated by TH2 immune responses to respiratory infections
What is urticaria?
hives. Itchy swellings caused by release of histamine by mast cells in the skin
What is angioedema?
inflammation caused by activation of mast cells in deep subcutaneous tissue. causes swelling that is more diffuse than observed in urticaria
What are the 3 strategies to reduce effects of allergic disease?
- modification of patient behavior
- pharmacological approach
- immunological treatment
What do drugs to treat allergic reactions usually consist of?
antihistamines, corticosteriods, cromolyn sulface and epinephrine
What do corticosteroids do?
suppress leukocyte function and used to treat chronic inflammation
What does cromolyn sulfate do?
used as a prophylactic inhalant; prevents degranulation of activated mast cells and granulocytes
What are examples of immunological treatments for allergic reactions?
desensitization by a series of injections to change the TH2 response to a TH1 response OR vaccinate patients with allergen-derived peptides to be presented by MHC class II molecules to TH2 CD4 cells in an attempt to induce anergy
What is the connection between people with parasitic diseases and allergic reactions?
people with parasite infections rarely develop allergic diseases because some parasites will purposely induce very potent immune responses to induce large non-specific IgE production so that the non-specific IgE will outcompete the parasite-specific IgE and prevent them from being attacked. This same mechanism reduced allergies
What type of hypersensitivity reactions produce hymolytic anemia and thrombocytopenia?
Type II
What type of hypersensitivity reactions are associated with reactions to drugs like penicillin, quinidien, and methyldopa?
type II hypersensitivity
Describe the mechanism of penicillin hypersensitivity reactions.
Penicillin will bind to surface of RBCs and create new epitopes which the immune system is not tolerant of. RBCs coated in complement and macros activated. Activated macros activate TH2 cells, which activate B cells to produce IgG. IgG binds to altered RBCs and stimulates complement activation and macrophage phagocytosis. RBCs are destroyed
which are more likely to cause type III hypersensitivity reactions: large immune complexes or small immune complexes?
small immune complexes are harder to clear and tend to precipitate more.
Large ones fix complement efficiently and are readily taken up by macros.
What is the name of the reaction when a type III hypersensitivity is purposely induced by injecting an IgG-antigen complex subcutaneously?
Arthus reaction - inflammatory response.
What is serum sickness?
result of immune responses to non-self material from infusion treatments. immune complexes build up and cause systemic inflammatory response. Causes chills, fever, rash, arthritis, vasculitis and sometimes glomerulonephritis.
What is farmer’s lung?
disease from exposure to inhaled pathogens that trigger IgG response instead of IgE response. after a while, immune complexes build up and cause type III hypersensitivity
What is bird-breeder’s disease?
inhalation of avian antigens that causes type III hypersensitivity
What is delayed-type hypersensitivity?
occurs 1-3 days after contact with antigen. require about 100-1000x the amount of antigen than allergic reactions do. Example: mycobacteria tuberculosis. Individuals who have been exposed to tuberculosis will react to a subcu injection within 3 days if they have TH1 response to it.
What type of hypersensitivity is poison ivy?
Type IV reaction. against pendacactechol
What are most allergens?
proteases
What is TNF-alpha?
pro-inflammatory cytokine
What do mast cells release during degranulation?
histamine, TNF-alpha, number of cytokines, leukotrienes, Platelet activating factor
