Hypersensitivity

Question 1

What is an antigen

Answer 1

Any molecule or molecular structure that can be recognised by an antibody or the adaptive immune system

Question 2

Differen structures of antibodies

Answer 2

Question 3

How do T cells differentiate

Answer 3

Question 4

What is type 1 hypersensitivity known as

Answer 4

Immediate or anaphylactic hypersensitivity

Question 5

What are types of Type 1 hypersensitivity

Answer 5

Asthma

Allergic rhinitis

Atopic dermatitis

Question 6

What is Type 1 hypersensitivity provoked by

Answer 6

Re-exposure to a specific type of antigen

Question 7

What are Type 1 hypersensitivity mediated by

Answer 7

IgE

Non allergic individuals only make IgE in response to parastic infections or potent venoms

Question 8

What are some different types of allergens

Answer 8

Food

plants

Due to multiple sites on antigen that antibody can stick onto

Question 9

How do you diagnose the allergy

Answer 9

Skin prick test

Wheal and flare

Question 10

End result of sensitization of the immune response to allergens

Answer 10

Type 2 help CD4 T cells

B cell helper follicular CD4 T cells

They both produce type 2 cytokines IL-4 and IL-13

These act on B cells

B cells therefore produce IgE

Question 11

Why are IgE rarely found in circulation

Answer 11

Normally bound to surface of innate immune cells, espeically mast cells and basophils

These granuloytic cells express high affinity IgE receptor (Fc epsilon receptor 1)

Question 12

What happens when an allergen is encountered by cell bound IgE

Answer 12

Rapid crosslinking and degradulation of mast cell or basophil

Happens much faster and across a much broader site

Question 13

Diagram of Hypersensitivity 1

Answer 13

Question 14

What is the end product of all hypersensitivity reactiosn

Answer 14

Release of histamine

Host of cytokines

Further Th2 differentiation

Highly active smooth muscle contracting

Question 15

What are the different phases of type 1 hpyersensitivity

Answer 15

Early phase: occurs within minutes

Later response: Recuitment of early inflammatory cells

Late response: Peaks 3-4 days after exposure where high frequencies of eosinophils are recruited

Question 16

What is Type 2 hypersensitivity referred to as

Answer 16

Antibody-mediated cytotoxic hypersensitivity

Question 17

Which antibodies are invovled

Answer 17

IgG and IgM

Question 18

Examples of Type 2 hyeprsensitivity

Answer 18

Mismatched blood transfuction

Haemolytic disease of newborns by transfer of antibodies across placenta

Immune thrombocytopenia (antibodies develop against platelet surface proteins)

Graves disease (thyroid stimulating antibodies (thyroid stimulating antibodies that bind to thyrotropin receptor)

Question 19

How does type 2 hypersentivity happen

Answer 19

Exposure to foreign antigen

Aberrant response to a self antigen

Question 20

What are the 3 mechanisms of Type 2 Hypersensitivity

Answer 20

1. Anti-receptor activity
2. Antibody dependent cell-mediated cytotoxicity
3. Classical activation of the complement cascade

Question 21

What is the complement cascade

Answer 21

Leads to MAC formation as well as inflammation opsonisation and recruimtment and activation of immune cells

Question 22

What happens in ADCC

Answer 22

In antibody-dependent cell mediated cytotoxicity antibody-antigen complexes on the surface of cells are bound by Fc receptors expressed by granulocytes and NK cells resulting in directed lysis

This releases inflammatory mediators, chemokines and cytokines

Question 23

Type 3 hypersensitivity is sometimes known as

Answer 23

Immune complex driven disease

Question 24

What are immune complexes

Answer 24

Non-cell bound antigen-antibody complexes which are normally cleared through the activity of the immune system

Question 25

What happens in Type 3 hypersensitivity

Answer 25

Immune complexes cannot be efficiently cleared e.g. antibodies reacting against self-antigens

Immuen complexes deposited in the blood vessel walls

Causes fever, rashes, joint pain or arthritis, glomerulonephritis

Question 26

What are some diseases of type 3 hypersensitivity

Answer 26

Rheumatoid arthritis

Multiple clerosis

Systemic lupus erythematosus (develop IgGs against DNA or proteins present in the nucleus of cells)

Question 27

How does serum sickness work

Answer 27

Anti-serum is given for snake venom (antibodies)

Body will react to produce antibodies against venom antibodies

Doesn’t cause a problem until person is bit again

Question 28

What is Type 4 hypersensitivity known as

Answer 28

Delayed-type or T cell mediated hypersensitivity

Question 29

Why is type 4 hypersensitivity slower

Answer 29

It is initiated by T cells

Antigen is presented to naive T cells by dendritic cell

Results in T memory cells

Subsequent exposure means they promot inflammation

Memory T cell response is slower than antibodies

Question 30

Examples of type 4 hypersensitivity (contact dermatits)

Answer 30

urushiol acts as a hapten

drives a T helper 1 response

Reexposure means that cytokines such as IFN-gamma are released

This promotoes pro-inflammatory activation of macrophages resulting in swelling and oedema

Question 31

What are examples of type 4 hypersensitivity

Answer 31

Nickel salt and hair dyes

Measles and mycobacerium tuberculosis

Question 32

How to test for TB

Answer 32

Injection of small amuonts of M.tb into skin (type 4 reaction)

Question 33

What Type 4 hypersensitivity can be related to others

Answer 33

Asthma ( T helper cells produce soluble mediators that promote bronchoconstriction)

Tissue graft rejection (CD8 T cells)

Question 34

Diagram of summary of hypersensitivity

Answer 34