The Immunology of Allergy

56 Pages·2016·1.78 MB·English

by  Nishit Shah

The Immunology
and its clinical implications
of Allergy
By Dr Priya Bowry Sikand
MBBS MRCGP DFFP DIC MSc(Allergy)
Back to the Basics….
•
Type 1 Objectives
Understand immunological mechanisms behind
•
Hypersensitivity reactions
Relate the science to the patient and the available
•
tests
Relate the science to therapeutics
defend
eliminate IMMUNE
Body must itself against invasion by foreign
SYSTEM
substance and it – uses the
innate immune response
non- specific acquired immune
Employs two tactics –
response specific
( response) and
memory
( response to specific foreign
substances, with )
•
Acquired Immune Response
Specific response: ability to recognise small structures
immunocompetent cells - .
(antigens/allergens) on surface of foreign invader by army of
•
T and B cells
B cells (humoral response) produce antibodies against
foreign substances(neutralizers, activate complement
•
system)
‘’NINJAS!’’,
T cells (cell-mediated immunity): respond to cells displaying
‘surface markers’. T cytotoxic cells – T helper cells
– release Cytokines - stimulate B cells; and regulatory T cells
• memory
- suppress T helper cells and maintain self tolerance
Uses (T helper cells): to improve responses to
subsequent exposures i.e. more prompt and powerful
response
INNATE IMMUNITY ADAPTIVE IMMUNITY
SPEED OF ONSET
Immediate (within ~ 3d lag
SPECIFICITY TO minutes)
ANTIGEN
Lower Higher
DIVERSITY OF RESPONSE
Lower Higher
POTENCY
Lower Higher
MEMORY (reacts quicker
to subsequent
No Yes
exposures)
Extracellular pathogen is present Intracellular pathogen is
present
Antigen binds to B cell Pathogen is phagocytosed
receptor by APC
B cell presents the Presentation of antigen Infected cell presents
antigen on MHC by APC antigen on MHC
Activate T helper CD4 Activate T helper CD4
Activate B cell to make plasma Activate macrophage Activate cytotoxic CD8 T cell
cell
Antibody production Phagocytosis of Pathogen Cell mediated cytotoxicity
ATOPIC
Why is the immunology important?
These patients are all
ATOPY
genetic
T 2 driven
H
Atopy is the predisposition to develop
environment
allergic diseases. It is characterised by a
resulting in IgE antibody responses.
(remember this also occurs in materno-foetal
phase to prevent rejection and for immunity
against parasitic diseases)
H
Normal individuals have T 1 driven responses and
do not react to innocent foreign substances in the
same way as an atopic.
The Allergic Reaction
•
inappropriate, exaggerated
Allergic diseases occur when the body makes an
innocent
response to seemingly
allergens
and common environmental or dietary
• IgE antibodies
substances, known as .
Production of against these allergens
result in inflammation (swelling, redness, itching,
irritation and watery discharge) and hence, disease.
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