Adverse immune reactions

Question 1

What are the 4 adverse immune reactions?

Answer 1

• Tolerance
• Autoimmunity
• Hypersensitivity
• Transplantation

Question 2

What is immune tolerance?

Answer 2

A state of unresponsiveness to a particular antigen
It is essential to prevent harmful immune reactivity to the bodies own tissues
Elimination of self-reactive cells

Question 3

Which 2 parts of the body are involved in central tolerance?

Answer 3

Thymus and bone marrow

Question 4

Describe post-thymic T-cell tolerance

Answer 4

• Self reactive T-cells abort
• Self reactive T-cells deleted
• Maintained by immune regulation

Question 5

What is Autoimmunity?

Answer 5

Loss of self, non-self discrimination which results in immune responses and damage to host tissues

Question 6

In what ways can autoimmunity arise?

Answer 6

• Exposure of hidden antigens
• Formation of new epitopes
• Cross reactivity with microorganisms
• Induction by viruses
• Immunoregulation deficiency

Question 7

In which sites is autoimmunity most likely to occur?

Answer 7

Sites that are not usually undergoing immune surveillance

• Brain
• Eye
• Repro tract
• gall bladder

Question 8

Give some organ specific autoimmune diseases

Answer 8

Muscles = Myasthenia gravis (dog)
Blood = Haemolytic anaemia 
Reproductive = Anti-sperm antibodies (Brucella)
Neuro = Polyneuritis

Question 9

Describe Myasthenia gravis

Answer 9

Autoimmune antibodies are produced against the acetylcholine receptor so muscle cannot respond to acetylcholine, resulting in muscle wastage

Question 10

Which immunoglobulin is produced in a type I hypersensitivity reaction?

Answer 10

IgE

Question 11

Compare a normal immunoglobin response to a type 1 hypersensitive response

Answer 11

Normal - IgM production in the primary response which switches to IgG/A production in the secondary response
Type 1 = gene deletion can lead to a switch to IgE production

Question 12

Give examples of type 1 hypersensitivities

Answer 12

Specific allergic conditions:

• Urticaria (skin rash)
• Milk allergy
• Food allergy
• Allergic inhalant dermatitis
• Parasite allergies
• Allergies to drugs/vaccines

Question 13

Describe a type II hypersensitive reaction

Answer 13

• Antibodies bind to antigens on host tissues or cells
• Tissue damage caused by frustrated phagocytes and compliment activation
• Triggers antibody dependent cell cytotoxicity

Question 14

Give 2 examples of Type II hypersensitive reactions

Answer 14

• A blood group issue in newborn foals

- Canine autoimmune haemolytic anaemia

Question 15

Describe a type III hypersensitive immune response

Answer 15

Immune complexes form or deposit on host tissues

• Excess antibody
• Activate compliment or trigger polymorphonuclear leukocytes to release destructive enzymes

Question 16

Which hypersensitive immune response is T-cell mediated?

Answer 16

Type IV

Question 17

Which hypersensitive immune response does not involve antibodies?

Answer 17

Type IV

Question 18

Describe a type IV hypersensitive response

Answer 18

Primed T-cells produce cytokines which attract and activate macrophages and these damage tissues by release of enzymes and other mediators

Question 19

When is a type IV hypersensitive response used?

Answer 19

Skin testing for TB in cattle

Question 20

Why are foreign tissues rejected in a transplant?

Answer 20

Differences in MHC I and II between the host and donor

Question 21

Why is a foetus regarded as the ultimate transplant?

Answer 21

50% of their tissues are foreign

Question 22

Give definitions of the following:

1. Autograft
2. Isograft
3. Allograft
4. Xenograft

Answer 22

1 = From one part of the body to another
2 = Between genetically identical individuals (twins)
3 = Between different members of the same species
4 = Between members of different species