hypersensitivity reactions and disease

Question 1

definition of a hypersensitivity reaction

Answer 1

Immune response that results in bystander damage to the self. Usually exaggeration of normal immune mechanisms

Question 2

type 1 hypersensitivity

Answer 2

immediate hypersensitivity

Question 3

type 2 hypersensitivity

Answer 3

direct cell effects

Question 4

type 3 hypersensitivity

Answer 4

immune complex mediated

Question 5

type 4 hypersensitivity

Answer 5

delayed type hypersensitivity

Question 6

allergic immune responses

Answer 6

type 1. cause atopic dermatitis, food allergy and allergic asthma. evolved to combat parasitic infection

Question 7

what response has to be triggered for it to be a true allergic reaction

Answer 7

IGE response

Question 8

what can trigger allergic reactions

Answer 8

house dust mite, pollen, foods, drugs, latex, bee and wasp venom

Question 9

adverse reactions

Answer 9

not all adverse reactions are allergic reactions, there are different protocols for allergic/adverse reactions

Question 10

why is the prevalence of allergies increasing

Answer 10

the hygiene hypothesis = we’re not exposed to a wide enough range of pathogens/antigens

Question 11

what occurs in the absence of parasitic infections but presence of innocuous substances

Answer 11

type 1 hypersensitivity reaction promotes allergic reactions

Question 12

what is Th2 differentiation stimuli

Answer 12

antibody mediated immunity. the default allergy system at birth, everything is dangerous. we’re programmed to have this system as at birth we’re susceptible to parasites.

Question 13

what is the Th1 allergy system

Answer 13

cell - mediated protective immunity. due to interactions with other people and materials no allergies are present. strong enough immune system

Question 14

What are the stages of the sensitisation stage of allergy

Answer 14

the naive t cells are stimulated by antigen and co stimulation (proliferation). they then differentiate into TH2 cells which regulate allergies and parasite infection

Question 15

what are the naive t cells stimulated by to cause proliferation

Answer 15

antigen and co-stimulation factor (dendritic cells)

Question 16

what do allergin specific t cells trigger

Answer 16

allergin specific IgE

Question 17

what is the Fc region

Answer 17

the tail end of the antibody

Question 18

which cells express receptors that bind with the Fc region during the sensitisation phase

Answer 18

mast cells and basophils

Question 19

what do B cells produce on their first encounter with the allergen

Answer 19

antigen specific IgE antibodies

Question 20

what happens during the pathological stage of allergy

Answer 20

re-encounter with the allergen

Question 21

what happens when the allergen binds to the IgE coated mast cells and basophils during pathological stage

Answer 21

degranulation

Question 22

what does degranulation include

Answer 22

release of vasoactive mediators (histamine, tryptase)

Question 23

what else is expressed during the pathological stage

Answer 23

increased expression of pro-inflammatory cytokines and leukotrienes

Question 24

what effect does histamine and serotonin have

Answer 24

increased vascular permeability : smooth muscle contraction

Question 25

what effect does tryptase have

Answer 25

bronchial mucus secretion, degradation of blood vessel basement membrane

Question 26

Management of IgE mediated allergic disorders

Answer 26

Avoidance of allergen
Block mast cell activation
Prevent effects of mast cell activation

Question 27

what mediates type II hypersensitivity reactions

Answer 27

IgM/IgG antibodies directed towards antigens present on cell surfaces or the extracellular matrix

Question 28

how do the antibodies deal with the reaction on type II

Answer 28

 destruction of antigen-positive cells (type IIa reactions)
or
 stimulation of cell surface antigens (type IIb reactions)

Question 29

how is type III mediated

Answer 29

by soluble immune complexes

Question 30

what is a soluble immune complex

Answer 30

molecule formed from the binding of multiple antigens to antibodies

Question 31

how does the type III reaction happen

Answer 31

A hypersensitivity reaction resulting from soluble antigen-antibody immune complexes passing between endothelial cells of the blood vessels and becoming trapped on the surrounding basement membrane = inflammation.

Question 32

what type of antigen triggers type II response

Answer 32

usually a self antigen (autoimmunity) or a small inhaled antigen

Question 33

what is the type IV reaction driven by

Answer 33

CD4 + T cells

Question 34

what are some of the classic hallmarks of type IV reactions

Answer 34

-The large number of macrophages at the reaction site
-That it takes an average of 24-48 hrs for symptoms to manifest after re-exposure to the initiating antigen
-Granulomas often form due to infectious pathogens/foreign bodies that cannot be cleared