Transcript Online Counseling Resource YCMOU ELearning Drive…

Online Counseling Resource
YCMOU ELearning Drive…
School of Architecture, Science and Technology
Yashwantrao Chavan Maharashtra
Open University, Nashik – 422222, India
OC-SBT052-CP3-04
Introduction
Programmes and Courses
 SEP–SBT052–Unit-03
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Credits
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Academic Inputs by
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Arun Punaji More.
M.Sc. (Microbiology)
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Experience: 11 Years
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[email protected]
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How to Use This Resource
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Counselor at each study center should use this presentation to deliver
lecture of 40-60 minutes during Face-To-Face counseling.
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Discussion about students difficulties or tutorial with assignments should
follow the lecture for about 40-60 minutes.
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Handouts (with 6 slides on each A4 size page) of this presentation should
be provided to each student.
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Each student should discuss on the discussion forum all the terms which
could not be understood. This will improve his writing skills and enhance
knowledge level about topics, which shall be immensely useful for end
exam.
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Appear several times, for all the Self-Tests, available for this course.
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Student can use handouts for last minutes preparation just before end
exam.
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Learning Objectives
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After studying this module, you should be able to:
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Describe the delayed type or type IV
hypersensitive reaction
Describe the mechanism of type IV
hypersensitive reaction
Describe the diseases involving type IV
hypersensitive reaction
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Introduction
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The type IV hypersensitive reaction mainly
involved in intracellular pathogens such as
Mycobacterium tuberculosis, Brucella,
Cryptococcus, Leishmania etc.
The type IV reaction is purely cellular in
its response i. e. it purely mediated by
sensitized cells only.
In this module students will learn the
important features of type IV
hypersensitive reaction and some
medically important diseases involving the
type IV hypersensitive reactions.
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Type IV Hypersensitive Reaction-1
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The type IV hypersensitive reaction
mainly are mediated by sensitized TH1
cells.
The delayed type hypersensitive reaction
usually remained localized and is
characterized by the influx of large
number of non specific inflammatory cells
such as macrophages.
The delayed type hypersensitive reaction
was first observed by Robert Koch in 1890
in individual infected with Mycobacterium
tuberculosis.
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Type IV Hypersensitive Reaction-2
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In delayed type hypersensitive (DTH)
reaction macrophages are mainly
recruited in inflammed tissues.
The main immune cells involved in
delayed type hypersensitive reaction are
various types of macrophages such as
Langerhans cells, dendritic cells.
Usually in delayed type hypersensitive
reaction tissue damages are limited and
the reaction play an important role in
defense against intracellular pathogens.
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Type IV Hypersensitive Reaction-3
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Mechanism:
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The DTH begin with initial sensitization of TH1
cells by a foreign antigen presented by
antigen presenting cells such as macrophages.
The activated TH cells clonally expand.
During the subsequent exposure of the same
antigen; these activated TH cells secrete
variety of cytokines that attract variety of
macrophages, non specific inflammatory cells
and activate them.
The activation of the macrophages take 24 48hr time.
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Type IV Hypersensitive Reaction-4
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Mechanism:The damages in type IV hypersensitive
reaction is mainly by overactivated
Macrophages by TH1 cells.
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Type IV Hypersensitive Reaction-5
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Mechanism:
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The activated macrophages at the site of their
recruitment carryout massive phagocytic
activity secreting large amount of lytic
enzymes which result in non specific
destruction of infected cells and thus killing of
intracellular pathogens.
Usually by DTH the intracellular pathogens are
cleared completely, however some time if the
antigens are not cleared completely, then
prolonged DTH response developed into visible
granulomatous reaction producing granuloma.
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Type IV Hypersensitive Reaction-6
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Mechanism:
The immune cells involved in type IV
hypersensitive reaction are
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Antigen presenting cells (APC)
TH1 cells
Macrophages
Cytotoxic T cells
The cytokines involved in type IV
hypersensitive reaction are
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IL-12 –secreted by antigen activated APC and
stimulate differentiation of naive T cells into
activated TH1 cells and increase production of
INF-γ by T cells.
INF-γ –secreted by T cells and NK cells and activate
macropahges.
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Type IV Hypersensitive Reaction-7
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Mechanism:-
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Type IV Hypersensitive Reaction-8
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Diseases involving DTH:
Tuberculosis:
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Pulmonary tuberculosis caused by Mycobacterium
tuberculosis is contained by cells mediated
immunity.
Delayed clearance of this infection develop DTH
resulting in formation of granuloma.
The infection can be diagnosed with the help of
DTH reaction by injecting PPD antigen derived
from cell wall of Mycobacteria intradermally.
The characteristic skin lesion developed at the
site of antigen injection showing positive DTH
reaction.
The positive DTH reaction on skin show that pre
exposure to mycobacteria.
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Type IV Hypersensitive Reaction-9
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Diseases involving DTH:
Contact dermatitis:
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It is development of inflammation on the skin
when sensitized skin come into contact with
chemicals such as nickel, turpentine,
formaldehyde, active agents in cosmetics and hair
dyes, poison oak, poison ivy.
When these chemical come into contact of skin
proteins they acquire antigenic properties and
internalized by skin macrophages which sensitize
the TH1 cells.
When the same chemical come into contact of
skin then sensitized TH1 cells. Mount DTH
response resulting in the development of contact
dermatitis.
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What We Learn…..
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Delay type hypersensitive reaction
Cells involved in DTH
Cytokines involved in DTH
Mechanism of DTH
Diseases involving DTH
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Critical Thinking Question
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Why INF-γ is essential in the development of
DTH?
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Hints For Critical Thinking Question
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INF-γ activate macrophages.
Enhance TNF production by macrophages
and epithelial cells.
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Study Tips
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Book
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Title: Immunology
Author: Richard A. Goldsby, Thomas Kindt,
Barbara A. Osborne.
Publication: W.H. Freeman and Company, New
York.
Book
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Title: Textbook of Microbiology
Author: R. Anathanarayan & C.K.J. Paniker
Publication: Orient Longman publication,
Chennai.
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End of the Presentation
Thank You !
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