allergies

Question 1

what is an allergy or hypersensitive reaction

Answer 1

immune response against innocuous antigen in a pre-sensitised host

Question 2

describe type 2 hypersensitive and its clinical features

Answer 2

cytotoxic
IgG and IgM response to antigen at cell surface attached to tissue

minutes to hours onset - cell lysis and necrosis

Question 3

what are common antigens and associated disease of type 2 hypersensitivity

Answer 3

penicllin

erythroblast fetalis - Rh- mother and Rh+ foetus - antibodies made - if another Rh + baby its attacked

good pastures nephritis

penecillin mediated autoimmune haemolytic anaemia

Question 4

describe type 3 hypersensitivity and its clinical features

Answer 4

immune complex

IgG and iGM against solum antigen - forms complex in organs which triggers complement pathway and self damage
commonly damages kidneys joints and extremities

onset 3-8 hours, vasculitis

Question 5

what are the traditional cause of type 3 hypersensitive and what are the associated disease

Answer 5

serum sickens due to tetanus

SLE

Question 6

describe type 4 hypersensitivity and the cancel features

Answer 6

delayed

antigen specific T cell mediated cytoxicity
antigen recognised by APC for primary exposure
subsequent exposure activates T cells causing cell damage due to cytokines

48-72 hours - erythema induration - patch test

Question 7

what are common antigens of type 4 hypersensitivity and what are he associated conditions

Answer 7

metals such as nickel - tuberculin reaction

contact dermatitis - patch testing

Question 8

what is an allergy a combination of

Answer 8

genetics and the environment

Question 9

what are the three immune response to parasitic disease

Answer 9

increased levels of IgE

tissue inflammation with basophil infiltration and eosinophilia/mastocytosis

presence of CD4+ t helper cells secreting cytokines

Question 10

what is the hygiene hypothesis

Answer 10

immune stimulation by microbes protects against allergies - so if microbes decrease then allergies increase

Question 11

how do infections protect you against allergies

Answer 11

TH1/TH2 balance deviation - antigenic competition

immune regulation

Question 12

what are some examples of genetic influence on the allergic immune response

Answer 12

polygenic disease
cytokine gene cluster Il3,5,9,13
FcERI
IFN / TNF

Question 13

describe IgE production

Answer 13

antigen is recognised by TH2 and B cell (APC) - TH2 uses IL-4 to signal B cells which drives B cell production of IgE for mast cells and offers support for proliferation

Question 14

what is an early priming event and what does it cause

Answer 14

decrease in barrier function allows allergen to access immune system - likely to increase risk of allergy developing

Question 15

how do T helper cells differentiate

Answer 15

begin as naive T CD4 t cell then detects antigen presenting cell and pathogen which then change into TH1/2/17 or Treg

Question 16

what is the primary cell mediator in type 1 Hypersensitivity and what is its role

Answer 16

TH2
multiple cytokine release - attracts innate inflammatory response but can cause tissue damage

drive for immunoglobulin production - B cell makes IgE which activates innate and adaptive reponse

Question 17

what are the clinical features of a type 1 hyper reaction

Answer 17

fast onset 15- 30 minutes

wheal and flare - anaphylaxis

Question 18

what is the late phase response of type 1 hypersesn

Answer 18

eosinophils
arachonidonic acid metabolised
mainly involved in asthma a

Question 19

what are the physiological changes of anaphylaxis

Answer 19

sudden onset, skin mucosal tissue or both

sudden respiratory symptoms or reduced BP or end organ dysfunction

Question 20

what is the difference in blood pressure reduction in a type 1 hypersesiivtiy reaction for children and adults

Answer 20

children - low systolic or greater than 30% decrease in SBP

adults - systolic BP less than 90 mmHg or greater than 30% decrease from baseline

Question 21

how would you treat a mild vs severe anaphylaxis

Answer 21

mild - antihistamines

severe - adrenaline pen

Question 22

what is the atopic triad

Answer 22

rhinitis
asthma
eczema (atopic dermatitis)

Question 23

what is rhinitis and how do you treat it

Answer 23

allergic - all year (perineal) or seasonal
blocked nose, runny, itchy - eye symps
animal dander, pollens

anti-histamines and nasal steroids

Question 24

what is asthma and what is the risk with damaged airways

Answer 24

inflammation and hyperactivity of small airways
IgE mediated and late response eosinophils

damaged airways = hyper-reactive to non-allergic stimulus such as cold air or smoke

Question 25

what is atopic dermatitis and how do you treat it

Answer 25

no local IgE
more autoimune type response - itching and cracking of skin - house dust mite

topical steroids and moisturisers

Question 26

describe the pathogenesis of asthma

Answer 26

allergen to apc
app to TH2
TH2 releases cytokines IL4/13 - B plasma cell and release IgE which targets mast cells
TH2 releases IL5 which activates eosinophils

Question 27

what are the tests for hypersensitivity

Answer 27

specific IgE in the blood - can provide false neg and pos

skin prick test - false neg and pos

intra dermal test

graded challenge test

basophil activation test - IgE binding means basophils unregulated expression of activation markers

Question 28

for most hypersensitivity reactions what is the general treatment

Answer 28

to treat symptoms - antihistamines steroids and adrenaline

specific - immunotherapy

Question 29

what is the mechanism in terms of cells changes in allergen specific immunotherapy

Answer 29

increases in TH2 and TH2 cytokines such as IL-10

reduced numbers of mast cells and their ability to release mediators

less eosinophils and neutrophils at site of allergen

Question 30

what specifically are major food allergens

Answer 30

water soluble glycoproteins 10-60kDa

Question 31

what are the clinical manifestations of food allergies

Answer 31

vomiting, diarrhoea, oral symps

rhinitis and bronchospasm

urticaria and angioodeema

anaphylaxis

Question 32

what do you need to ask about with the history of a drug allergy

Answer 32

indication of the drug
detailed description of the reaction
time between drug and onset
number of doses taken before onset

Question 33

what is the management of drug allergies

Answer 33

intradermal testing as skin isn’t sensitive enough
dermal graded challenge
desensitisation - keep living does to exhaust mast cells