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SC246: Fundamentals of Microbiology
Unit 8 Seminar:
The Immune System
Evelyn I. Milian
Instructor
Microbiology: Unit 8 Seminar – The Immune System
Seminar Application Questions
1. The Complement system is an important part of the innate immune system that has
far-reaching effects on the body’s ability to fight off infection. Many pathogens have the
ability to affect or disable individual proteins within the Complement system. In your
opinion, which Complement protein (C5a? C1?) would be most devastating to the
host immune system if it were to be inactivated by a particular pathogen? Why?
2. As you have learned in this unit, the immune system does an exceptional job in clearing
infections from the host. However, on occasion the immune system can actually make an
illness worse by overreacting to a potential pathogen. One example is a phenomenon
called “cytokine storm”. This occurrence takes place when the body is infected by
specific pathogens. Some examples include the influenza virus that caused the 1918
Spanish Flu epidemic and more recently the SARS epidemic in 2003. What occurs
during “cytokine storm” and how does it affect the host? Find an example of a
more recent disease (hint: look at the flu virus) that induces cytokine storm.
3. Human society has evolved significantly over the past few decades. Populations of
humans used to inhabit wide-open spaces and rarely had contact with large crowds of
people. However, modern society requires people to live in very tight quarters and come
into contact with possibly hundreds or thousands of people in a single day. Consider cities
like New York City and Tokyo, Japan. Occupants in these cities are packed in tightly into
subway systems and overcrowded conditions. When people in Japan are ill, they wear
face masks to protect others, while in New York City this is not done. What are some
other ways that people in these cities (and other large cities around the world) deal
with potential exposure to pathogens?
Eve lyn I . Milian - Instructor
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Microbiology: Unit 8 Seminar – The Immune System
 Innate or nonspecific immunity (nonspecific defenses)
 Body’s defenses against any kind of pathogen (microorganism capable of
causing disease); they are present in our bodies at birth.
 Adaptive, acquired or specific immunity (specific defenses)
 Body’s defenses against specific pathogens. Acquired immunity adapts or
adjusts to handle a particular microbe. These defenses are obtained during
the life of the individual. Unlike innate immunity, adaptive immunity is slower
to respond, but it has a memory component.
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Microbiology: Unit 8 Seminar – The Immune System
Blood Cells
(Formed Elements)
 Blood contains
erythrocytes (red blood
cells) and leukocytes
(white blood cells).
 The second line of
defense of the innate
immunity includes
phagocytes, white blood
cells that engulf and
digest microorganisms or
other particles that are
harmful to the body
(phago = eat; cyte = cell).
 Macrophages,
neutrophils, dendritic
cells, eosinophils
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Microbiology: Unit 8 Seminar – The Immune System
Stages of the Mechanism
of Phagocytosis
1)
2)
3)
4)
5)
Chemotaxis: chemically
stimulated movement of
phagocytes to a site of
damage.
Adherence: attachment
of the phagocyte to the
microbe or foreign material.
Ingestion: phagocyte
engulfs the microbe
(forming a phagosome).
Digestion: phagocyte
releases lysozyme and
digestive enzymes to
degrade the microbe.
Killing and Discharge:
the chemical substances
released by the phagocyte
kill the microbe and waste
material is discharged.
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Microbiology: Unit 8 Seminar – The Immune System
Innate Immunity – Second Line of Defense:
INFLAMMATION
 Inflammation is a nonspecific defensive host
response to tissue damage characterized by
the following signs and symptoms:
 Redness
 Pain
 Heat
 Swelling (edema)
 Inflammation can also cause loss of function
sometimes, depending on the site and extent
of the injury.
Eve lyn I . Milian - Instructor
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Microbiology: Unit 8 Seminar – The Immune System
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Microbiology: Unit 8 Seminar – The Immune System
Eve lyn I . Milian - Instructor
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Microbiology: Unit 8 Seminar – The Immune System
Innate Immunity – Second Line of Defense:
ANTIMICROBIAL SUBSTANCES: The Complement System
 The Complement System is a group of plasma proteins that activate one
another to help destroy invading microorganisms.
 Complement proteins are activated in a cascade, a set of reactions that amplify
some effect—that is, more product is formed in the second reaction than in the
first, still more in the third, and so on. Complement is activated in several ways.
Eve lyn I . Milian - Instructor
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Microbiology: Unit 8 Seminar – The Immune System
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Microbiology: Unit 8 Seminar – The Immune System
C
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Microbiology: Unit 8 Seminar – The Immune System
The Result of Complement Activation
Eve lyn I . Milian - Instructor
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Microbiology: Unit 8 Seminar – The Immune System
The Result of Complement Activation
(a) C3a and C5a bind to mast cells, basophils, and platelets to trigger the release
of histamine, which increases blood vessel permeability.
(b) C5a functions as a chemotactic factor that attracts phagocytes to the site of
complement activation.
Eve lyn I . Milian - Instructor
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Microbiology: Unit 8 Seminar – The Immune System
Application:
Question Number 1

The Complement
system is an
important part of the
innate immune system
that has far-reaching
effects on the body’s
ability to fight off
infection. Many
pathogens have the
ability to affect or
disable individual
proteins within the
Complement system.
In your opinion,
which Complement
protein would be
most devastating to
the host immune
system if it were to
be inactivated by a
particular pathogen?
Why?
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Microbiology: Unit 8 Seminar – The Immune System
Innate Immunity – Second Line of Defense:
ANTIMICROBIAL SUBSTANCES: The Complement System
 Complement deficiencies can
result in an increased
susceptibility to disease.
 Some bacteria evade destruction
by complement by means of:
 capsules, surface lipid-
carbohydrate complexes,
and enzymatic destruction of
C5a (the fragment that serves
as a chemotactic factor that
attracts phagocytes).
Eve lyn I . Milian - Instructor
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Microbiology: Unit 8 Seminar – The Immune System
Innate
Immunity:
Innate
Immunity:
Nonspecific
Defenses of
the Human
Body
Nonspecific
Defenses of
the Human
Body
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Microbiology: Unit 8 Seminar – The Immune System
Adaptive Immunity Includes Antibody-Mediated Immunity (Humoral Immunity by B Cells)
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Microbiology: Unit 8 Seminar – The Immune System
T-Cells and Cell-Mediated Immunity
 Cytokines: small proteins made by
body cells (including lymphocytes and
APCs) that act as chemical
messengers in the immune system
affecting the behavior of other cells,
such as macrophages and T cells.
 Cytokines stimulate or inhibit cell growth
and differentiation, regulate immune
responses, or aid nonspecific defenses.
 Cytokines directly or indirectly may
induce fever, pain, and the proliferation
of T cells.
Eve lyn I . Milian - Instructor
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Microbiology: Unit 8 Seminar – The Immune System
Evelyn I. Milian - Instructor
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Microbiology: Unit 8 Seminar – The Immune System
Application – Question Number 2
 As you have learned in this unit, the immune system does an
exceptional job in clearing infections from the host. However,
on occasion the immune system can actually make an
illness worse by overreacting to a potential pathogen. One
example is a phenomenon called “cytokine storm”. This
occurrence takes place when the body is infected by specific
pathogens. Some examples include the influenza virus that
caused the 1918 Spanish Flu epidemic and more recently
the SARS epidemic in 2003.
 What occurs during “cytokine storm” and how does it
affect the host? Find an example of a more recent
disease (hint: look at the flu virus) that induces
“cytokine storm”.
Eve lyn I . Milian - Instructor
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Microbiology: Unit 8 Seminar – The Immune System
Cell-Mediated Immunity: Cytokine Storm
 A cytokine storm (hypercytokinemia) is a
potentially fatal immune reaction consisting of
elevated release of cytokines.
 Normally, the release and action of cytokines is
kept in check by the body. However, sometimes
the reaction becomes uncontrolled, and too
many immune cells are activated at once. This
event can lead to severe damage to body
tissues and organs.
 The precise cause is not fully understood, but
some triggers of cytokine storm may include:
 Avian influenza virus (H5N1), Swine flu virus
(H1N1; 2009 outbreak), graft versus host
disease, sepsis
Eve lyn I . Milian - I nstructor
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Microbiology: Unit 8 Seminar – The Immune System
Application – Question Number 3
 Human society has evolved significantly over
the past few decades. Populations of humans
used to inhabit wide-open spaces and rarely
had contact with large crowds of people.
However, modern society requires people to
live in very tight quarters and come into contact
with possibly hundreds or thousands of people
in a single day. Consider cities like New York
City and Tokyo, Japan. Occupants in these
cities are packed in tightly into subway systems
and overcrowded conditions. When people in
Japan are ill, they wear face masks to protect
others, while in New York City this is not done.
 What are some other ways that people in
these cities (and other large cities around
the world) deal with potential exposure to
pathogens?
Evelyn I. Milian - Instructor
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Microbiology: Unit 8 Seminar – The Immune System
Tracking Disease in the Population: Public Health Organizations
 Centers for Disease Control and
Prevention (CDC): a branch of the U.S.
Dept. of Health and Human Services (with
headquarters in Atlanta, GA). Website:
www.cdc.gov.
 Collects and analyzes epidemiological
information in the United States.
 Publishes “Morbidity and Mortality
Weekly Report” (MMWR).
 World Health Organization (WHO):
international agency in Geneva,
Switzerland. Website: www.who.int/en/
 Coordinates and sets up programs to
improve health in more than 100
member countries.
 Publishes “Weekly Epidemiological
Record”.
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Microbiology: Unit 8 Seminar – The Immune System
References
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Bauman, Robert W. (2012). Microbiology with Diseases by Body System. Third
Edition. San Francisco, CA: Pearson Education, Inc.-Benjamin Cummings.
Black, Jacquelyn G. (2005). Microbiology, Principles and Explorations. Sixth Edition.
NJ: John Wiley & Sons, Inc. www.wiley.com/college/black.
Campbell, Neil A.; Reece, Jane B., et al. (2011). Campbell Biology. Ninth Edition.
San Francisco, CA: Pearson Education, Inc.-Pearson Benjamin Cummings.
Cowan, Marjorie Kelly; Talaro, Kathleen Park. (2009). Microbiology A Systems
Approach. Second Edition. New York, NY: The McGraw-Hill Companies, Inc.
www.mhhe.com/cowan2e
Dennis Kunkel Microscopy, Inc. (2011). http://www.denniskunkel.com
Mader, Sylvia S. (2010). Biology. Tenth Edition. NY: The McGraw-Hill Companies, Inc.
Martini, Frederic H.; Nath, Judi L. (2009). Fundamentals of Anatomy & Physiology.
Eighth Edition. San Francisco, CA: Pearson Education, Inc. – Pearson Benjamin
Cummings.
Tortora, Gerard J.; Derrickson, Bryan. (2006). Principles of Anatomy and
Physiology. Eleventh Edition. NJ: John Wiley & Sons, Inc.
www.wiley.com/college/apcentral.
Tortora, Gerard J.; Funke, Berdell R.; Case, Christine L. (2010). Microbiology An
Introduction. Tenth Edition. San Francisco, CA: Pearson Education, Inc.-Pearson
Benjamin Cummings. www.microbiologyplace.com.
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