Hypersensitivity Flashcards
What is hypersensitivity?
Excessive immune response that cause damage
What can cause hypersensitivity?
Infectious agents
Environment
Self antigens
Are all infectious agents capable of triggering hypersensitivity?
No
Give an example of a virus which causes hypersensitivity.
Influenza
Can trigger major cytokine secretion
Give an example of an environmental substance which may trigger hypersensitivity.
Dust
May enter lower respiratory tract, trigger antibody response
Which Ig is associated with farmer’s lung?
IgG
What happens when environmental substances are small enough to diffuse through skin?
Can trigger delayed hypersensitivity response
What can Nickel do on contact?
Contact dermatitis
What is the onset of type I hypersensitivity like?
Rapid onset
IgE mediates adaptive immune response
Mast cell and eosinophils mediate innate immune response
What is the onset of type II hypersensitivity like?
Rapid onset
IgG mediates adaptive immune response
Complement and phagocytes mediate innate immune response
What is the onset of type III hypersensitivity like?
Slow onset (hours)
IgG mediates adaptive immune response
Complement and neutrophils mediate adaptive immune response
What is the onset of type IV hypersensitivity like?
Very slow onset (2-3 days)
T cell mediates adaptive immune response
Macrophages mediate innate immune response
What kind of hypersensitivity is peanut and dust allergies?
Type I
Environmental triggers
What kind of hypersensitivity is Farmer’s lung?
Type III
Environmental trigger
What kind of hypersensitivity are immune haemolytic anaemias?
Type II
What kind of hypersensitivity is SLE?
Type III
Autoimmune issue
What kind of hypersensitivity is Coeliac disease?
Type IV
What kind of hypersensitivity is contact dermatitis?
Type IV
What kind of hypersensitivity usually mediates allergy?
Type I
Describe the process of Type I hypersenitivity.
Environmental factors
TH2 cells produce IL4 which induces production of IgE
Mast cell degranulation
What does atopy mean?
Basically another word for allergy
Immediate hypersensitivity reactions mediated by IgE
Can atopy be inherited?
Yes
Atopy traits can be passed on
May not be same allergy as parents
What is the allergen in penicillin allergy?
Beta-lactam
What are some symptoms of systemic allergy?
Low BP
Angioedema
Airway obstruction
What are some symptoms for allergy in the airways?
Reversible bronchial obstruction Discharge Sneezing Nasal obstruction Allergic conjunctivitis
What are some symptoms of allergic reactions on the skin?
Itchy oedema
Lip swelling
Itchy inflammation
What does filaggrin do?
Maintain epithelial barriers, moisturising surfaces and controlling pH
What is filaggrin?
Protein expressed by keratinocytes
What do mast cells produce?
Prostaglandins and leukotrienes through COX and lipo-oxygenase pathways
Does allergy raise or lower BP?
Lower
Often severe drop
Is there mucus secretion in asthma?
Yes
Contributes to airflow obstruction
How do we test for allergies?
Skin-prick
Positive control could be histamine and negative control could be saline
What is anaphylaxis?
Mast cells and leukotrienes produced Vasodilation and increased vascular permeability Fluid shifts to extra-vascular space Fall in vascular tone Drop in BP Mast cells release histamines
What is Rhesus?
IgG develops during pregnancy and crosses placenta
Causes haemolytic disease
What is the most common cause of hyperthyroidism?
Graves disease
Which gene is associated with Graves disease?
HLA allele DR3
How are large complexes cleared?
Broken down by complement
What is a possible cause of slow complex formation in nephrotic syndrome?
Hep B
What is a possible cause of rapid complex formation in nephrotic syndrome?
Strep infection
Describe immune complex disease in the kidney.
Common cause of renal failure
Glomerulonephritis including nephrotic syndrome and nephritis
What is nephrotic syndrome?
Protein leaks into urine
Gradual development
Renal failure
How does nephritis present?
Rapid onset renal failure
Blood and protein in urine
Hypertension
What role does Tissue Necrosis Factor play in hypersensitivity?
Secreted by macrophages and T cells and causes much of the tissue damage in delayed hypersensitivity
How does hypersensitivity affect RA?
TH1 and TH17 infiltrate synovium
TNF and IL-17 attract neutrophils which damage synovium
How do inflammatory cells affect MS?
TH1 and TH17 cells and macrophages develop in the affected nervous tissue
The inflammatory lesions cause the reversible, relapsing disability typical of early MS