allergies

Question 1

describe the induction phase (sensitization) of allergies

Answer 1

allergen (normally harmless protein) is captured by antigen presenting cells
presents allergen antigen to T cells
T helper cells produce IL4,2,13 to stimulate B cells to differentiate to plasma cells and produce igE antibodies.

Question 2

describe the reactive phase of allergies

Answer 2

with subsequent exposure to allergen igE antibodies on mast cells bind to allergen
leading to mast cell degranulation releasing histamine, leukotrienes, prostaglandins and chemotactic factors.
this leads to:
vasodilation>oedema>hives (on skin)
bronchoconstriction > asthma (at lungs)
mucus production > rhinitis (at nasal passages)

Question 3

how are allergies identified

Answer 3

intradermal skin prick tests with liquid allergen

Question 4

what are the roles of histamine

Answer 4

H1 receptors
contraction of smooth muscle (ileum, airways and uterus)
dilation of BV
increased permeability of capillaries
causes itching sneezing and pain on sensory nerves
in the CNS causes wakefulness
goblet cells increased mucus secretion

H2 receptors
acid secretion in stomach
HR increase

H3 receptors
presynaptic, inhibit NT release

H4
uhhh idk inflammation

Question 5

what are symptoms and causes of allergic rhinitis

Answer 5

causes:
1. perennial ex: dust mites
2. seasonal ex: hay fever
3. occupational ex: latex
4. atopy (genetic predesposition)

symptoms
1. nasal itching
2. rhinorrhoea (runny nose)
3. sneezing
4. conjunctival symptoms (itchy red eye)

Question 6

describe the mechanism of action of H1 antagonists

Answer 6

blocks H1 receptors so that histamine cant interact and produce allergic effects. remove symptoms of rhinitis except for nasal obstruction.

sedating:
chlorphenamine
alimemazine
promethazine
(penetrate BBB)

non sedating:
acrivastine
cetrizine
fexofenadine
loratadine
(dont cross BBB)

topical: azelastine nasal

Question 7

give examples of nasal decongestants

Answer 7

cause nasal vasoconstriction to reduce swelling and mucus flow (which cause nasal blockages)
ex: a adrenoceptor agonists (intranasal)
xylometazoline a2 agonist
phenylephrine a1 agonist

rebound congestion needs to be used for less than 7 days (possibly due to sm fatigue)

Question 8

describe anaphylaxis and its treatment

Answer 8

severe allergic reaction that causes:
bronchoconstriction (Tightness of throat)
vasodilatation (drop in BP)
itchiness
puffy face and tounge

treatment:
oxygen
fluids to increase BP
adrenaline to increase bronchodilatation and cardiac output
b2 adrenoceptor agonist
H1 antagonist
steroid

Question 9

describe the MOA of chromones

Answer 9

used nasally and for eyes
mast cell stabilisers (inhibit degranulation)
ex: sodium cromoglicate and nedocromil sodium

Question 10

describe the MOA of steroids

Answer 10

drug crosses plasma membrane and acts at glucocorticoid receptor.
receptor dimerizes and crosses the nuclear membrane to reduce the transcription of inflammatory genes and increase the transcription of anti-inflammatory genes.
(reduce cytokines and chemokines)