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