hypersensitivity

Question 1

define antigen

Answer 1

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

Question 2

what is type 1 hypersensitivity?

Answer 2

an allergic reaction provoked by re-exposure to a specific type of antigen referred to as an allergen.

Question 3

give some example of diseases which arise from type i hypersensitivity

Answer 3

.asthma
.atopic dermatitis
.allergic rhinitis

Question 4

what mediates type 1 hypersensitive reactions

Answer 4

IgE

Question 5

what can diagnose allergies

Answer 5

skin prick test

Question 6

what is the end result which causes the sensitisation of the immune response to allergens causing IgE production

Answer 6

.generation of type 2 helper CD4 T cells
B cell helper follicular CD4 T cells ( B CELLS THAT ASSOCIATE WITH DENDRITIC CELLS AND NEED T CELLS TO ALLOW DIFFERENTIATION)

Question 7

B cell helper follicular CD4 T cells ( T cell that activates the B cell) causes production of which type 2 cytokines

Answer 7

IL 4, IL13

Question 8

When type 2 cytokines IL 4 and IL 13 act on B cells, what happens

Answer 8

promote B cell to switch to producing antigen specific IgE.

Question 9

true or false:IgE is very rarely found in the circulation, even in allergic individuals

Answer 9

true

Question 10

which cells does IgE particularly rapidly bind to

Answer 10

mast cells and basophils (innate immune cells)

Question 11

what happens if an allegern is encountered by a cell bound IgE?

Answer 11

rapid crosslinking and degranulation of the mast cell or basophil.

Question 12

end products of type 1 reactions

Answer 12

release of histamine, a host of cytokines that can recruit other cells and promote further Th2 differentiation, and highly active smooth muscle contracting molecules such as leukotrienes and prostaglandins.

Question 13

what is the early phase?

Answer 13

a result of bioactive small molecules produced directly by mast cells, occurs within minutes of allergen exposure

Question 14

what is the later response

Answer 14

later response, is the result of the recruitment of early inflammatory cells such as neutrophils.

Question 15

what is the late response

Answer 15

where high frequencies of eosinophils are recruited and Th2 cells are present.

Question 16

what is type II hypersensitivity?

Answer 16

involves the destruction of cells by IgG or IgM antibody bound to antigens present on the surface of the cells.

Question 17

Give examples of type ii hypersensitivity

Answer 17

hameolytic diseases of newborns
immune thrombocytopenia- where antibodies develop against platelet surface proteins

Graves disease where patients develop thyroid stimulating antibodies that bind the thyrotropin receptor resulting in secretion of thyroid hormones.

Question 18

list the three mechanisms in which antibodies cause disease

Answer 18

Anti-receptor activity – blocking or activating its function
Antibody dependent cell-mediated cytotoxicity (abbreviated to ADCC)
Classical activation of the complement cascade

Question 19

what is the complement cascade?

Answer 19

a complex process by which antibody on the surface of cells is recognised by the complement components, ultimately leading to the formation of the membrane attack complex (MAC) in the surface of the cell, and cell death due to loss of osmotic integrity.

Question 20

what can activation of the complement cascade result in?

Answer 20

inflammation,
opsonisation

recruitment and activation of immune cells.

Question 21

n ADCC antibody-antigen complexes on the surface of cells are bound by…

Answer 21

Fc receptors

Question 22

Fc receptors are expressed by

Answer 22

cells such as granulocytes and NK cells

Question 23

binding of the ADCC antibody-antigen complex to Fc receptors leads to…

Answer 23

directed lysis of the target cell, but also the release of inflammatory mediators, chemokines and cytokines.

Question 24

type 2 hypersensitivity can lead to…

Answer 24

ocal or systemic inflammation, cell depletion leading to a loss of function or imbalance in organ function.

Question 25

what are immune complexes?

Answer 25

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

Question 26

what happens if immune complexes aren’t cleared?

Answer 26

complexes end up being deposited in the blood vessel walls and tissues, promoting inflammation and tissue damage.

Question 27

what symptoms arise from immune complexes not being cleared?

Answer 27

Fever
rashes
joint pain
protein in urine
vasculitis (blood vessel)
glomerulonephritis (kidney)
arthritis (joints)

Question 28

what autoimmune disorders arise from type 111 hypersensitivity

Answer 28

rheumatoid arthritis
multiple sclerosis
systemic lupus erythematosus (SLE)

Question 29

what is type IV hypersensitivity

Answer 29

involves T cell-antigen interactions that cause activation and cytokine secretion requiring SENSITIZATION of lymphocytes

Question 30

give 2 examples of type IV hypersensitivity

Answer 30

dermatitis
turburcular regions
graft rejections

Question 31

what causes dermatitis

Answer 31

caused by exposure to poison ivy, where a small molecule called urushiol acts as a hapten (and binds to proteins in the skin), drives a T helper 1 response