Immune Reponses Help Protect
the Body Against Disease
LEARNING OBJECTIVES
1.
Identify
the components of innate immunity.
2.
Explain
how cell-mediated immunity works.
3.
Outline
the process of antibody-mediated im-
munity.
4.
Describe
how vaccination protects the body
from disease.
icrobes and pathogens are all around you; ev-
ery day you come into contact with millions
of them. While you’re performing simple
activities such as brushing your teeth, shav-
ing, handling paper, or running your hand along a surface,
pathogens can enter into your body. How does the lym-
phatic system protect you?
Your body has two types of immune responses that can
defend against disease.
Innate immunity
is a series of non-
specific physical and chemical defenses.
Adaptive immunity
involves a specific reaction to patho-
gens called antigens. An
antigen
is
any substance that the immune sys-
tem recognizes as foreign (nonself).
Entire microbes or parts of microbes
may act as antigens. Chemical components of bacterial struc-
tures are antigenic, as are bacterial toxins and viral proteins.
Other examples of antigens include chemical components of
pollen, foods (such as egg white), drugs, incompatible blood
cells, and transplanted tissues and organs.
Antigens induce plasma cells
to secrete proteins
known as
antibodies,
as we will see soon. In fact, the word
antigen means antibody
g e n e r a to r .
In adaptive immunity,
antigens are presented to lymphocytes that respond by
antigen
(AN-ti-jen)
A substance that has
the ability to provoke
an immune response.
The first line o f in n ate im m unity • Figure 12.6
Skin
The epidermis is a physical
barrier to microbes.
Skin’s sebaceous (oil) glands
form acidic film that prevents
growth of microbes.
Skin’s sweat glands produce
sweat that flushes away
microbes.
Nose and mouth
Hairs like those in the nose filter
dust and microbes.
Mucus like that in the nose traps
microbes, while ciliated cells
move them away.
Saliva washes microbes from
tooth surfaces and mucous
membranes in the mouth.
Eyes
The lacrimal apparatus secretes
tears that dilute and wash away
irritants and microbes.
Physical barriers:
Chemical barriers:
• The epidermis, hair, and mucus.
• Lysozyme, an antimicrobial agent that is present in sweat, nasal
• Fluids that wash pathogens away.
secretions, salvia, tears, and tissue fluids.
• The acidic film produced by the skin’s sebaceous glands.
350 CHAPTER 12
The Lymphatic System and Immunity
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