chapter 15 Flashcards
exaggerated immune response that causes damage to the individual
hypersensitivity
an exaggerated immune response mediated by antibody or antigen-antibody complex that manifest with minutes to hours after exposure to antigen
immediate hypersensitvity
A type sensitive response mediated TH cells, which release various cytokines and chemokines. The response generally occurs 2-3 days after TH cells interact with antigen
Delayed-type hypersensitivity (DTH)
-responsible for type I hypersensitivity
-allergies are initiated by an interaction between an _____ antibody and a multivalent antigen
IgE
How do Ige antibodies act?
-by cross-linking Fcε receptors on the surfaces of innate immune cells
-granule contents are released
A type I hypersensitivity reaction is induced by certain types of antigens referred to as ____________________.
allergens
What does it mean if someone has atopy?
they are predisposed to generate IgE antibodies against common environmental antigens
The high-affinity IgE receptor, FcεRI
-responsible for most allergy symptoms
-found on basophils and mast cells
The low-affinity IgE receptor, FcεRII
regulates production of IgE by B cells
Histamine:
-accounts for 10% of granule weight
-binds to one of four possible histamine receptors
induces contraction of intestinal and bronchial smooth muscles,
increased permeability of venules, and mucous secretion
H1 binding
increases vasopermeability and vasodilation, stimulates exocrine
glands, and increases stomach acid; also suppresses degranulation of mast cells/basophils in a negative feedback loop
H2 binding
Leukotrienes and prostaglandins:
-Secondary mediators―formed when membrane phospholipids are enzymatically cleaved
-more potent stimulators of vascular permeability and mucous secretion
–considered to be a major cause of asthma symptoms
stimulate TH2 responses to increase IgE production by B cells
IL-4 and IL-13
recruits and activates eosinophils
IL-5
may contribute to shock in systemic anaphylaxis
TNF-α
acts as a chemotactic factor, attracting other cells
IL-8
stimulates production and activation of more myeloid cells, including more granulocytes
GM-CSF
Type I early responses:
-occur within minutes of allergen exposure
-Mediated by mast cell granule contents
Type I late responses:
-occur hours later, a result of recruited cells
-Often inflammatory cell types such as neutrophils
Type I 3rd phase?
-starts three days after exposure, peaks at four days post-exposure
-Characterized by massive eosinophil infiltration
a serious allergic reaction that is rapid in onset and may cause death
Anaphylaxis
Systemic Anaphylaxis:
-a shock-like and often fatal state, the onset of which occurs within minutes.
-Venom from bee, wasp, hornet, and ant stings; drugs such as penicillin, insulin, and antitoxins; and seafood and nut.
-Epinephrine is the drug of choice
results from inhalation of common airborne allergen, such as
pollen
Allergic rhinitis (hay fever)
the reaction developed in the low respiratory tract.
asthma
an inflammatory disease of skin that is frequently associated
with a family history of atopy
Atopic dermatitis (eczema)
cause upper or lower gastrointestinal tract smooth muscle contraction
resulting in vomiting or diarrhea
food allergies
Allergy-linked genes include:
-Proteins involved in generation and regulation of immune
responsiveness
* Innate immune receptors
* Cytokines/chemokines and their receptors
* MHC proteins
- Airway remodeling genes
* Growth factors
*Proteolytic enzymes
- Transcription factors and proteins regulating epigenetic
modifications also implicated
In a skin test, what indicates an allergic response?
swelling and redness
Hyposensitization:
-Repeated low-dose exposures may induce an increase in regulatory T cells and their cytokines
-May also induce competitive IgG subtypes
bind and block H1 receptors on target cells
antihistamines
________________________antagonists work in a manner similar to antihistamines
leukotriene
inhibit innate immune cell activity in airways, treating asthma
Inhalation corticosteroids
the hygiene hypothesis:
-exposure to some pathogens early in life provides a better T-cell balance
-Avoids dominance of TH2 subset, which promotes IgE production by B cells (stimulating allergic responses)
-May explain why countries with improved hygiene
are experiencing increases in asthma and allergy
rates
transfusion reactions are a type of ____________________________hypersensitivity reactions
antibody mediated type II
What happens if someone receives a transfusion with the wrong type of blood?
their antibodies will quickly attach to the donor blood cells and trigger
complement proteins
Describe Immune complex-mediated (type III) hypersensitivity:
-May trigger release of inflammatory mediators and vasoactive mediators (recruit neutrophils)
– Proteases released may damage connective tissues
– Clots may form as complexes activate platelets
* Symptoms include fever, rashes, joint pain, lymph node
enlargement, and protein in the urine
Describe Delayed-type (type IV) hypersensitivity (DTH):
-Purely cell-mediated rather than Ab mediated
-Initiated by T cells
-Requires a delay for the reaction to develop
-Characterized by recruitment of macrophages at inflammation site
-Poison ivy contact dermatitis is the most common example
The initiation of a type IV DTH response involves ______________ by
an antigen.
sensitization
The __________________ phase of a classical DTH response is induced by
second exposure to a sensitizing Ag.
effector
Describe what happens during the second exposure of a DTH response:
-TH1 inflammatory cytokines are produced that recruit and help activate macrophages
A prolonged activation of macrophages leads to ___________ formation
granuloma
A prolonged inability to clear antigens can result in formation of destructive_______________________________________________
multinucleate giant cells and granulomas
Contact dermatitis is a type _________ hypersensitivity response
IV
