Overview of the Immune System
(Class 1)
Ed Ishiguro
Department of Biochemistry and Microbiology
And
The UVic Speakers Bureau
Major function of immune system
• Offers protection against infectious
diseases
• Caused by bacteria, viruses, fungi (molds),
parasitic worms, etc.
Some essential facts about
microorganisms
• Most abundant and diverse forms of life on earth
• Found everywhere and impossible to avoid
• Vast majority are non-pathogenic
• Healthy humans naturally colonized by enormous number of microorganisms, mostly bacteria (we are 10 times microbial)
Main properties of innate and acquired
(adaptive) immunity
Innate Acquired
Nonspecific Pathogen-specific
Rapid response Slow initial
response
No memory of
previous encounter
Retains memory of
first encounter
Relative time courses and activities of
innate and acquired immune responses
Rela
tive i
mm
un
e a
cti
vit
y
Days
Innate
Acquired
Arrows indicate times
of microbial challenge
Primary response
Secondary response
All blood cells derived from bone marrow “stem cell”
Innate immunity
Phagocytes (dual function)
Acquired immunity
(NK = “Natural Killer”)
The immune system = “white blood cells”
Cells of immune system reside
in lymphatic (green) and
circulatory (red) systems
Figure 24.2, Brock Biology of Microorganisms, 14th ed.,
Pearson Education, Inc., 2015
Circulatory and lymphatic vessels are interconnected
(Circulation throughout body) (Circulation through lungs)
Immune cells migrate through
blood and lymph
Figure 24.2, Brock Biology of Microorganisms, 14th ed., Pearson Education, Inc., 2015
Overview of Innate Immunity
Innate immunity is the first line of
defense: non-cellular components
• Physical barriers: skin and mucus
secretions
• Antimicrobial proteins in tissues and
secretions– Our natural antibiotics designed for indiscriminate
killing of any microbial threats
11
Innate immunity is the first line of
defense: cells of immune system
• Natural killer (NK) cells
• Phagocytes (also participate in acquired
immunity): e.g., macrophages and
neutrophils
12
Natural killer cells recognize and kill
abnormal cells
Infection (or any cause of tissue damage)
induces inflammation (a protective strategy)
(immune
cell)
Chemicals that
mediate symptoms
of inflammatory
reaction, e.g., fever,
edema, redness, etc.
Infection (or any cause of tissue damage)
induces inflammation, cont’d
“vaso”: from Latin
meaning vessel
More innate immune
cells, e.g., neutrophils,
attracted to site by
chemicals released by
phagocyte
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