hypersensitivity

Question 1

what type of hypersensitivity is asthma?

Answer 1

type 1 (allergic reaction provoked by re-exposure to a specific type of antigen)

Question 2

hallmarks of type II hypersensitivity?

Answer 2

antibody-mediated cytotoxic

destruction of cells by IgG or IgM antibodies

complement pathway etc

Question 3

hallmarks of type III hypersensitivity

Answer 3

immune complex driven disease

when immune complexes are not effectively cleared

serum sickness (snake bite)

Question 4

what are immune complexes

Answer 4

non cell bound antigen/antibody complexes

Question 5

symptoms of type III

Answer 5

fever rashes joint pain protein in urine vasculitis glomerulonephritis arthritis

Question 6

autoimmune disorders w type III

Answer 6

rheumatoid arthritis, MS, SLE (lupus)

SLE- IgGs developed against DNA or proteins

Question 7

type IV

Answer 7

delayed type, T-cell mediated hypersensitivity

Question 8

Rate limiting step of all hypersensitivity reaction?

Answer 8

Antigens

Question 9

What is a hapten

Answer 9

A small molecule which is not antigenic on its own but can form an antigen when associated with a large carrier like a protein

Question 10

Which hypersensitivity reaction causes a characteristic “wheal and flare”

Answer 10

Type 1

Question 11

What happens in type 1 hypersensitivity when IgE binds to the surface of innate immune cells eg mast cells

Answer 11

Rapid cross linking and degranulation of mast cells/basophils

End product is the release of histamine, also leukotrienes and prostaglandins

Question 12

What do leukotrienes and prostaglandins do?

Answer 12

They are smooth muscle contracting molecules

Question 13

What are the phases of response of a type 1 reaction?

Answer 13

Early phase- caused by bioactive small molecules produced directly by mast cells within minutes of allergen exposure

Later phase- recruitment of early inflammatory cells like neutrophils (few hours later)

Late response- peaks 3-4 days after exposure, high frequencies of eosinophils are recruited, Th2 cells present

Question 14

Examples of type II hypersensitivity reactions

Answer 14

Mismatched blood transfusion
Haemolytic disease of newborns
Immune thrombocytopenia- antibodies against platelet surface proteins
Graves’ disease - thyroid stimulating antibodies developed

Question 15

3 possible mechanisms of type II hypersensitivity reactions?

Answer 15

1- anti-receptor activity (blocking/activating function)
2- antibody dependent cell-mediated cytotoxicity (ADCC)
3- classical activation of the complement cascade

Question 16

Results of type II reactions

Answer 16

Tissue injury eg local/systemic inflammation, cell depletion leading to a loss of function/ imbalance in organ function

Question 17

what’s an immune complex

Answer 17

an antibody which is bound to its antigen

Question 18

what is immunogenicity?

Answer 18

the ability of a substance to elicit an immune response

Question 19

what are DAMPs?

Answer 19

molecules released as a result of non-apoptotic cell death

Question 20

what are PAMPs?

Answer 20

common molecular patterns found in pathogens and microbes but not in host cells (normally)

Question 21

what do PRRs do?

Answer 21

host proteins which recognise DAMPs and PAMPs and activate the innate immune system

Question 22

what is a type 1 response mediated by?

Answer 22

antigen specific IgE antibodies

Question 23

what is the process of IgE production in type 1 responses?

Answer 23

due to genetics, environment etc..

CD4 cells produce cytokines which act on B cells, causing them to produce IgE

Question 24

which type of hypersensitivity reaction is also known as antibody-mediated cytotoxic hypersensitivity?

Answer 24

type II