Hypersensativity

Question 1

What is true of all hypersensitivity reactions?

Answer 1

Must have been exposed to the antigen prior to the reaction.

Question 2

What kind of hypersensitivity is associated with Type I reactions?

Answer 2

Anaphylaxis

Question 3

What are the cytokines and transcription factors involved in Type I hypersensitivity?

Answer 3

APC’s presenting to T-cell with IL-4 and induces GATA-3 to become TH2, then releases IL-4 and IL-5. causing creation of IgE.

Question 4

What are the cytokines and molecules released upon activation of the mast cells in Type I?

Answer 4

• Histamine
• Tryptase**
• Leukotrienes
• Thromboxane

Question 5

What can be tested for after a reaction to confirm it was anaphylaxis?

Answer 5

Tryptase - can be measured up to 4 hours after event, it’s either presents or not.

Question 6

What causes the late phase response after an anaphylaxis reaction?

Answer 6

After initial response of the mast cells begin producing cytokines for the eosinophils, but this takes between 4-6 hours to occur.

• IL-4/IL-13 – class switching
• IL-3 / GM-CSF
• **- IL-5, promotes survival and migration of eosinophils

Question 7

What are the chemokines that are released in the late phase reaction?

Answer 7

• MIP-alpha (CCL3)
• RANTES (CCL5)
• Leukotrienes

Question 8

What drug therapeutics can be used to block the leukotrienes?

Answer 8

Zileuton, blocks the production of leukotrienes

Zafirlukast, blocks the receptors

Question 9

How can mast cells threshold for granular release be modified?

Answer 9

Promotes: Cytokines and Histamine
Suppresses: Glucocorticoids and Antihistamine

Question 10

What are the common reasons Eosinophil counts can be elevated?

Answer 10

• Neoplasm
• Asthma
• Allergy
• Connection Tissue Disease
• Parasites

Question 11

Other than anaphylaxis, what are other clinical symptoms of Type I hypersensativity?

Answer 11

• Asthma
• Rhinitis
• Urticaria

Question 12

What is the cause and risk factor for asthma?

Answer 12

When the IgE cross links to a certain antigen in the airways and causes local reaction.
Being hospitalized at a young age increases risk for developing asthma.
–Asthma attacks are when eosinophils release and the leukotrienes contract the smooth muscle and the air can’t escape the lungs.

Question 13

What is the cause of Type II hypersensativity?

Answer 13

IgG or IgM binding to matrix bound antigens, then immune cells bind to Fc receptors causing local tissue damage. Also when drugs bind to cells the combined matrix can mount an immune response.

Question 14

What kind of hypersensativity reaction when the response to strep antigen cross reacts with heart valves and joints?

Answer 14

Type II Hypersensativity, Acute Rheumatic Fever

Question 15

What is the cause of Type III Hypersensitivity?

Answer 15

IgG react to soluble antigens causing complexes of antibodies to get stuck in low flow areas causing local immune responses and damage.

Question 16

What are the most common areas of damage in Type III Hypersensitivity?

Answer 16

• Kidneys
• Joints
• Vessels
• Skin

Question 17

What is an Arthus reaction?

Answer 17

• Skin reaction in an individual that has been exposed to an antigen, mast cells activated in the skin.

Question 18

When does serum sickness occur 7-10 days after exposure to the antigen?

Answer 18

The antigen the individual was exposed to is still residing in the body slowly getting degraded by macrophages, but an immune response has mounted and when the IgM->IgG switch occurs they will become symptomatic due to the remaining antigen present. IgG has higher affinity forming more complexes.

Question 19

What is the mechanism of Type IV Hypersensitivity with Rhus Dermatitis?

Answer 19

Antigen penetrates the skin, picked up by dendritic cell, then presents to TH1 CD4+ cell, which activate by secreting: IFNalpah, TNF, GM-CSF, Chemokines

• -This recruits Macrophages to the site causing localized inflammation and symptoms.
• *Must be to a previously exposed antigen**

Question 20

How does the TB test utilize this principle?

Answer 20

The TB protein is injected under the skin and if the body has seen TB before it will cause a localized inflammatory response within 48hours after recruitment by Th1 cells.

Question 21

What hypersensitivity reactions involve complement and how?

Answer 21

Type II - Complement can bind the matrix bound complexes causing recruitment of immune cells
Type III - Complement binds the complexes, both promoting their degradation and recruitment of others.

Question 22

What is the role of Eotaxin and who produces it?

Answer 22

Eotaxin is a chemokine that binds to Eosinophils only and is found in areas of allergic inflammation.
RANTES also binds to the same receptor.