hypersensitivity

Question 1

hypersensitivity

Answer 1

is a state of altered reactivity in which the body reacts with and exaggerated immune response to a foreign agent

Question 2

allergy

Answer 2

is an example of type one hypersensitivity

allergen = an antigen that causes and allergic reaction

Question 3

hapten

Answer 3

small molecules e.g dust that require a protein carrier to elicit an immune response

Question 4

atopy

Answer 4

genetic predisposition for allergy

Question 5

type 1 hypersensitivity

Answer 5

mediated by IgE
most common and rapid response to allergens
can result in anaphylaxis

Question 6

describe the process of type 1 hypersensitivity

Answer 6

APC processes allergen and presents it to naive t cell
This t cell now tells B cells presenting the antigen to class switch and produce IgE antibodies
These antibodies bind to Fc receptors on mast cells and basophils
Subsequent binding of allergen to IgE antibodies causes degranulation and release of inflammatory mediators

Question 7

what cascade produces anaphylatoxins

Answer 7

complement cascade

Question 8

what are 4 methods for testing allergy

Answer 8

skin prick - skin pricked with small amount of allergen
patch test - tests if reaction is due to skin contact by taping small amount to skin via metal discs
blood test - measures IgE levels
oral challenge - ingests suspected allergen and response measured

Question 9

3 anti allergen drugs

Answer 9

anti-histamines - compete with histamine for receptors
hydrocortisone - blocks histamine synthesis
epinephrine (epi-pen) - immediate treatment for anaphylactic shock, reverses effects of histamine i.e vasodilation and relaxes muscles

Question 10

cutaneous atopy

Answer 10

localised allergy e.g hayfever, atopic dermatitis

Question 11

systemic anaphylaxis

Answer 11

anaphylactic shock throughout the entire body

Question 12

type II hypersensitivity

Answer 12

involves activation of complement system by IgG or IgM binding to an antigenic cell (either an allergen/ hapten or auto antigens)

Question 13

how are cells lysed in type II hypersensitivity

Answer 13

membrane attack complex formation - antibody activates complement system which leads to this
antibody dependent cell mediated cytotoxicity - antibodies attract immune cells that bind via Fc receptors and destroy the cell

Question 14

example of type II hypersensitivity

Answer 14

transfusion of mismatched blood

Question 15

what is the main difference between type II and type III hypersensitivity

Answer 15

Type III involves neutrophils

Question 16

type III hypersensitivity

Answer 16

involves reactions against soluble antigens circulating in serum

Question 17

example of type III hypersensitivity

Answer 17

arthus reaction

oral erythema multiforme (crusty blistering of oral mucosa)

Question 18

type IV hypersensitivity

Answer 18

t cell mediated and involves no antibodies
involves both CD4 and CD8 t cells
delayed reaction due to time needed to recruit t cells
OFG is a potential example