VMED 5172 - Hypersensitivity

Mast cells and eosinophils

Type I hypersensitivity is mediated by what cell types?

Type II

Which hypersensitivity type is associated with antibodies?

Immune complexes and neutrophils

Type III hypersensitivity is associated with what immune cells?

Type IV

Which type of hypersensitivity is mediated by T cells?

IgE receptors

What type of immunoglobulin is seen in a mast cell associated hypersensitivity?

Within seconds to minutes; mast cells are located close to the skin

A type I hypersensitivity reaction happens within what timeframe? Why is this?

Degranulation

Once an allergen binds to a mast cell, what process occurs which leads to symptoms?

Anaphylaxis

A systemic, life-threatening reaction to an allergen is known as?

Lungs

In most domestic animals, the 'shock organ' is the?

Dogs

In which species is the shock organ considered to be the liver?

Hepatic veins constrict, causing blood backup and systemic hypotension, leading to circulatory collapse

Physiologically, how does the liver cause death via anaphylaxis?

Atopy

An exaggerated response to environmental antigens is known as?

Sensitization and elicitation

The development of a type I hypersensitivity requires what steps?

Activation of B cells and isotype switching to IgE takes at least two weeks

Why do signs of a type I hypersensitivity reaction not appear upon first exposure?

Atopic dermatitis, asthma, food allergies, allergic conjunctivitis/rhinits

What clinical issues are associated with type I hypersensitivity?

Type I

This is an example of what type of hypersensitivity?

Anti-inflammatories and antihistamines

When allergen avoidance is not possible, what treatment is recommended for type I hypersensitivity reactions?

Desensitization, or allergen specific immunotherapy

What process can be used to reduce the severity of a hypersensitivity reaction?

Increased quantities of an allergen are administered to an animal in order to reduce the subsequent severity of a reaction

Describe the process of allergen specific immunotherapy

The number of mast cells and IgE decreases, and mediator release from mast cells is decreased

What effect does increase dosage of an allergen have on an immune response?

Via an antibody binding to either self or foreign cells

How are type II hypersensitivity reactions triggered?

The complement is activated and the immune response destroys normal cells

Once an antibody binds to a cell and induces a hypersensitivity reaction, what is the effect on the body?

May cause destruction of newborn's red cells if these antibodies are ingested in milk; hemolytic disease of the newborn

When mothers make antibodies against fetal red cells, it can have what effect on a newborn? What is this called?

Different erythrocyte antigens are expressed on red cells of different types, and individuals may make antibodies against these antigens without prior exposure

Why do reactions to differing blood types occur?

IgM

What immunoglobulin type is associated with hypersensitivity in blood transfusions?

Transplacental hemorrhage or repeated pregnancies

In order for neonatal isoerythrolysis to occur, a mother's response to the fetal blood antigen must be boosted via?

Immune mediated hemolytic anemia

Some drugs and infectious agents can bind to red blood cells and cause lysis as a part of what disease?

An antibody and its bound antigen

Immune complexes are formed by what components?

Lattices

Type III hypersensitivity can result when the correct ratio of antigen to antibody is present and ___ form

Local and systemic reactions

What are the forms of type III hypersensitivity reactions?

Within tissues

Local type III hypersensitivity reactions are caused by immune complexes formed where?

Systemic

What form of type III hypersensitivity is characterized by immune complexes forming within the bloodstream?

Neutrophils, complement, etc.

In a local type III hypersensitivity reaction, there is activation of what immune cells locally?

Type III; triggered by infusion of anti-tetanus toxoid or anti-snake venom

Which hypersensitivity reaction type is 'serum sickness'? What is this triggered by?

If immune complexes get deposited in glomeruli, it can cause damage to the endothelium, which is worsened by neutrophils, leading to decreased kidney function

How can type III hypersensitivity reactions affect the kidney?

Delayed

Type IV hypersensitivity is also known as ___ hypersensitivity

T cells get activated and attack all antigen, even if it is bound to self cells

How is a type IV hypersensitivity reaction triggered?

Feet, ventral abdomen, neck region

Contact hypersensitivity is often seen on what areas of the body?

A

Which one of the following is an example of peripheral tolerance?

A. Preventing an immune response to harmless food allergens in the gut

B. Certain bacteria blocks the T cell receptors in the skin so that T cell does not recognize the antigen

C. T cells attack the blood cells in hemolytic anemia

D. In bone marrow, immature B cells undergo negative selection if their B cell receptors (BCRs_ strongly recognize self-peptides

B

Which of the following is an example of molecular mimicry?

A. Autoantibodies generated after a breach of the blood-brain barrier

B. Antibodies generated against Trypanosome cruzi cross-react with cardiac myocytes

C. Hypersensitivity reaction caused by poison ivy

D. Removal of aged red blood cells by the reticuloendothelial system