Immunopathology - Allergy & Hypersensitivity

Question 1

Which immunoglobulin types are involved in type II and III hypersensitivity?

Answer 1

IgM and IgG

Question 2

What is the target of the antibodies in type II hypersensitivities?

Answer 2

cell bound or extracellular matrix antigens

Question 3

What happens in type III hypersensitivities?

Answer 3

there is an immune complex deposition that can’t be cleared efficiently

Question 4

What is the main damage caused by complement in immunopathology?

Answer 4

the inflammation due to the production of C3a and C5a

Question 5

What are the two outcomes of type II hypersensitivity?

Answer 5

injury due to activation of effector mechanisms e.g. recruitment of inflammatory mediators and abnormal physiological responses due to activating or inhibiting receptors

Question 6

What is a transfusion reaction?

Answer 6

a type II hypersensitivity where the antibodies in the blood attack antigens on the red blood cells that have been transfused

Question 7

What are the consequences of a transfusion reaction?

Answer 7

RBC haemolysis, shock, nausea, vomiting, pain

Question 8

What antibodies are in the blood of a type A?

Answer 8

B

Question 9

What happens in a type II mediated drug allergy?

Answer 9

the drug will bind to RBCs and platelets and if the body produces antibodies against the drug then the splenic macrophages will phagocytose the cells resulting in haemolytic anemia or thrombocytopenia

Question 10

What happens in haemolytic disease of the newborn?

Answer 10

In the first pregnancy the mother is Rh-ve and the baby is Rh+ve, when the baby is born foetal blood cells enter the mother’s circulation and the mother makes antibodies against them. In the second pregnancy if the baby is Rh+ve the antibodies that the mother has made will cross the placenta and attack the RBCs of the foetus

Question 11

How is haemolytic disease of the newborn treated?

Answer 11

Give antibodies to the mother to clear the foetal RBCs from circulation before she makes an immune response

Question 12

What is Goodpasture’s syndrome?

Answer 12

where antibodies are generated against type IV collagen and the complement and phagocyte activation causes glomerular disease

Question 13

What is Grave’s disease?

Answer 13

where antibodies are generated which activate the receptor on the thyroid gland and cause hyperthyroidism

Question 14

What is myasthenia gravis?

Answer 14

where antibodies block the ability of ACh to bind to the NMJ causing muscle wasting

Question 15

What does the pathology of type III hypersensitivities depend on?

Answer 15

where the immune complexes are deposited

Question 16

How are immune complexes usually removed?

Answer 16

in the spleen by resident macrophages

Question 17

Why are immune complexes not cleared?

Answer 17

when there is an excess of antigens, the antibodies are low affinity and there is poor complement activation

Question 18

What is the mechanism of type III hypersensitivity?

Answer 18

there is a gradual deposition of immune complexes, and once it reaches a threshold there is enough to activate complement which leads to the induction of inflammatory mediators and an inflammatory response

Question 19

What is the outcome if the immune complexes deposit on blood vessel walls?

Answer 19

vasculitis

Question 20

What is the outcome of the immune complexes deposit on glomerular basement membranes?

Answer 20

glomerulonephritis

Question 21

What is the outcome if the immune complexes deposit on joint synovium and vessels?

Answer 21

arthritis

Question 22

What are the causes of type III hypersensitivity?

Answer 22

either persistent infection, autoimmunity or an inhaled antigen

Question 23

What is farmer’s lung?

Answer 23

localised immune complex in the lung due to exposure to bacteria in mouldy hay (actinomyces) - causes alveolitis leading to inflammation and fibrosis

Question 24

What is systemic lupus erythematosis?

Answer 24

defined by presence of anti-DNA autoantibodies and immune complex deposition in kidney - involves multiple body systems - cause is unknown

Question 25

Why do we make antibodies against self?

Answer 25

because antigen receptors are generated in a random way and although there are mechanisms to remove receptors that are reactive to self sometimes these dont work

Question 26

What are the two forms of immunological tolerance?

Answer 26

central tolerance - removal of self reactive lymphocytes at the site of development and peripheral tolerance - removal of self reactive lymphocytes outside site of development