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Immunization Competency Course - v 1.0
Module 2 - Immune System
May 2012
Page 1
Module 2
The Immune System
1.
Competency ............................................................................................................ 2
2.
Learning Objectives ................................................................................................. 2
3.
Introduction.............................................................................................................. 2
4.
Immune Defense ..................................................................................................... 2
5.
Lymphatic System ................................................................................................... 5
6.
Development of the fetal and neonatal immune system ........................................... 6
7.
Summary ................................................................................................................. 6
8.
Required Reading.................................................................................................... 7
9.
References .............................................................................................................. 7
10. Quiz ......................................................................................................................... 7
11. Quiz Answers .......................................................................................................... 9
Immunization Competency Course - v 1.0
Module 2 - Immune System
May 2012
Page 2
1. Competency
Demonstrate a general understanding of the immune system.
2. Learning Objectives
By the end of this module you will be able to:
 Compare and contrast innate and adaptive immunity.
 Differentiate between passive and active immunity.
 Describe the lymphatic system.
 Describe the development of the fetal and infant immune system.
3. Introduction
Knowledge of the basic functions of the immune system is useful in order to
understand how vaccines work and so you can provide recommendations on their
use.
4. Immune Defense
4.1 Overview
The body is protected from infectious agents and other harmful substances by a
variety of cells and molecules that make up the immune system.
Immunity is the ability of the human body to tolerate the presence of material
indigenous to the body (self), and to eliminate foreign (non-self) material. The
discriminatory ability provides protection from infectious disease, since most
agents or associated toxins are identifies as foreign by the immune system.
4.2 Immune Response to an Infection
The immune response responds at the site of the infection and at the lymph
nodes away from the infection. We can understand the immune response by
following the course of an infection.
 Barriers:
Most pathogens are kept outside of the body by protective mechanisms such as
tears, stomach acid and cilia
 Pathogen enters the body:
When there is an injury to tissue, bacteria or viruses can enter the tissue and
cause an infection
 “Innate” cells respond
Cells, such as macrophages and dendritic cells, in the tissues are specialized in
engulfing (phagocytosis) the invader.
 Dendritic cells get to work
Dendritic cells engulf the pathogen, present the antigen on their cell surface and
then travel to the lymph node.
Immunization Competency Course - v 1.0
Module 2 - Immune System
May 2012
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 T-Cells and B-Cells “adapt” to presenting antigen
In the lymph node the T-Cells are activated by the dendritic cells. The T-Cells
activate the B-Cells to make antibodies
 “Adaptive Immunity” kills invader
The T-Cells and antibodies return to the site of infection and help kill the
pathogen.
4.3 Immune System
To understand how vaccines work, you need to know how the immune system
learns to recognize and eliminate micro organisms that cause infectious disease.
Use Figure 1 and the following document to learn more about each component of
the immune system:
 Nova Scotia Immunization Manual:
http://www.gov.ns.ca/hpp/cdpc/info-for-professionals.asp
Immunization Competency Course - v 1.0
Module 2 - Immune System
May 2012
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Figure 1: Immune Defense
ANTIGENS
Infection
Physiologic
And
Chemical
Immunization
IMMUNE DEFENSE 1
Innate Immunity
Cellular/Phagocytosis
Active Immunity
Passive Immunity
Molecular
Injected
IMMUNE DEFENSE 2
Maternal
Adaptive Immunity
Cells
T cells
Cellular
(cell mediated)
immunity
T Cell
DEPENDENT
Response
B cells
Humoral
immunity
T Cell
INDEPENDENT
Response
Antibodies
IgM
IgG
IgA
IgE
IgD
Immunization Competency Course - v 1.0
Module 2 - Immune System
May 2012
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5. Lymphatic System
The cells of the immune system are transported throughout the body via the lymphatic
circulatory system. Lymph bathes the tissues of the body, and the lymphatic vessels collect
and move it eventually back into the blood circulation. Lymph nodes are found throughout the
lymphatic vessels and provide meeting areas for the immune system cells.
The lymphatic system contains the following:
 Primary Lymphoid Organs: bone marrow, thymus, lymphatic vessels
 Secondary Lymphoid Organs: lymph nodes, spleen
Figure 2 - Lymphatic System
Immunization Competency Course - v 1.0
Module 2 - Immune System
May 2012
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6. Development of the fetal and neonatal immune system
The development of the immune system occurs early in the fetal development. Newborns
(even premature infants) can actively distinguish self from non-self.
6.1 Fetal Development
Passive Immunity
Active Immunity
 Passage of maternal antibodies - IgG
only
 B-Cells and T-Cells are present by 14
weeks gestational age (GA)
 Beginning at 8 weeks gestational age
(GA)
 Relatively sterile environment in utero.
Enormous unchallenged immune
system capacity.
 Levels of IgG correlate with GA
 Low until 20 weeks GA
 By 40 weeks GA, the IgG
doubles that of 32 weeks GA
6.2 Neonatal and Infant Immunity
Birth
 Instant challenge
 Within hours after
birth the
gastrointestinal
tract is heavily
colonized
Passive Immunity
(maternal antibodies)
Active Immunity
 Circulating placental
IgG lasts 6 months or
longer
 B-Cell responses are good.
Until two (2) years of age the
child’s immune system does not
respond well to T-Cell
independent antigens (i.e.,
polysaccharides)
 Secretory IgA in
breast milk and
colostrum
 T-Cells: Responds well to T-Cell
dependent antigens (i.e.,
proteins)
7. Summary
The immune system is a complex coordination of organs, cells and proteins. Innate and
adaptive immunity work together to recognize self from non-self.
Immunization Competency Course - v 1.0
Module 2 - Immune System
May 2012
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8. Required Reading
 Nova Scotia Immunization Manual:
http:/www.gov.ns.ca/hpp/cdpc/info-for-professionals.asp
9. References
Nova Scotia Immunization Manual:
http:/www.gov.ns.ca/hpp/cdpc/info-for-professionals.asp
10. Quiz
Question #1
What term is best described as "The first line of defence against anything recognized
as non-self"?
A. Passive Immunity
B. Active Immunity
C. Adaptive Immunity
D. Innate Immunity
Question #2
Antibodies from breast milk are an example of which one of the following immunities?
A. Passive Immunity
B. Active Immunity
C. Adaptive Immunity
D. Innate Immunity
Immunization Competency Course - v 1.0
Module 2 - Immune System
May 2012
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Question #3
Which one of the following is a correct statement regarding IgM?
A. The most abundant immunoglobulin making up approximately 80% of all
antibodies in serum
B. The first immunoglobulin made following antigen exposure and is relatively shortlived
C. The only immunoglobulin that reaches the thymus gland and under goes
differentiation to become T-Cells
D. The main secretory immunoglobulin in breast milk, saliva, tears, and respiratory
secretions
Question #4
At birth, an infant's immune system is only able to recognize and respond to a limited
number of organisms at any one time.
A. True
B. False
Immunization Competency Course - v 1.0
Module 2 - Immune System
May 2012
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11. Quiz Answers
Question #1
Answer: D
Innate Immunity is the first line of defence against anything recognized as non-self.
Question #2
Answer: A
Antibodies from breast milk is an example of Passive Immunity.
Question #3
Answer: B
IgM is the first immunoglobulin made following antigen exposure and is relatively shortlived.
Question #4
Answer: False
Infants are capable of generating both humoral and cellular immune response to
pathogens at the time of birth.