Hypersensitivity and Autoimmunity

Question 1

define hypersensitivity

Answer 1

normally beneficial components of immune system act in an exaggerated or inappropriate fashion to environmental antigens which do not normally cause tissue damage

Question 2

how many mechanisms of hypersensitivity are there

Answer 2

4

Question 3

explain early and late phase allergenic responses

Answer 3

early: - within minutes
- preformed mast cell mediators
late: - hours
- newly synthesised mediators

Question 4

atopy

Answer 4

a genetic tendency to produce IgE to normally harmless, common environmental agents

Question 5

what is the clinical expression of an atopic tendency?

Answer 5

allergic reaction

Question 6

what is a immune complex made up of?

Answer 6

antigen and antibodies

Question 7

Autoimmunity

Answer 7

immune system mistakenly attacks itself :(

Question 8

explain what occurs in type III hypersensitivity

Answer 8

intermediate complexes are not absorbed by phagocytes, and can enter the blood vessels and attach to blood vessel walls, activating complements. Complements attract neutrophils, neutrophils degranulate releasing enzymes responsible for tissue damage

Question 9

explain what is meant by localised and systemic typeIII hypersensitivity

Answer 9

localised - mediated by IgG bound to modified cell surfaces

systemic - complexes of antibodies bound to poorly catabolised antigens

Question 10

role of haptens in type IV hypersensitivity

Answer 10

when bound to carrier protein produce antibodies which specifically bind to it

Question 11

define role of carrier protein in type IV hypersensitivity

Answer 11

necessary for hapten to attach to to produce sufficient antigenic bulk

Question 12

immunological intolerance

Answer 12

immune system avoids producing damaging reactions against self-antigens

Question 13

how does immunological intolerance arise?

Answer 13

deletion of auto reactive t&b cells during cell maturation, or by inhibiting them when they escape cell tolerance process

Question 14

aetiology

Answer 14

cause of disease

Question 15

factors involved in aetiology of autoimmune disease

Answer 15

• genetic (predisposition)
• immune regulatory factors
• hormonal
• environmental
• other (e.g. age)

Question 16

compare the effector mechanisms in autoimmune disease to those present in normal immune response

Answer 16

they are identical

Question 17

explain the spectrum of clinical disorders

Answer 17

disorders are normally organ specific or non-organ specific. it is common for a patient to have multiple disorders at one end of the system, but rare to have disorders form different ranges on the spectrum