HUMAN BIOLOGY

168 Chapter 9

active immunity Immunity
that develops after a person
receives a vaccine, which
stimulates the immune
system to produce anti-
bodies against a particular
pathogen.

immunotherapy Clinical
therapy that uses immune
system cells or substances
to treat disease.

interferon Type of cytokine
released by cells that are
infected by a virus. Unin-
fected cells may respond
by producing substances
that prevent the virus from
multiplying.

monoclonal antibody
Antibodies made in the lab-
oratory by cells cloned from
a single plasma (B) cell.

passive immunity
Immunity conferred by
injected antibodies to
a pathogen. It does not
stimulate the recipient’s
immune system to produce
antibodies.

vaccine Prepared sub-
stance that contains an
antigen. Most vaccines are
made using dead or weak-
ened antigens.

immunology in Everyday Life

may be helped by injections of antibodies that confer

passive immunity. A patient receives antibodies that have

been purified from another source, preferably someone

whose adaptive immune system already has produced

a large amount of the antibody. The result is “passive”

immunity because the recipient’s own B cells are not

n Modern science has developed powerful weapons that can

enhance the immune system’s functioning or harness it in

new ways to prevent or treat disease.

vaccination stimulates

immunity

Vaccination (“immunization”) is

a way to increase your immunity

against a specific disease. A vaccine

is a prepared substance that contains

an antigen. A vaccine is injected

into the body or taken orally, some-

times according to a schedule (Table

9.3). The first injection elicits a pri-

mary immune response that confers

active immunity. A later booster

shot elicits a secondary response,

in which more effector cells and

memory cells form. The booster can

provide long-lasting protection.

Many vaccines are made from

killed or extremely weakened patho-

gens. For example, weakened polio-

virus particles are used for the Sabin

polio vaccine. Worldwide vaccina-

tions with a weakened relative of

the smallpox virus allowed a suc-

cessful global effort to eradicate the

disease (Figure 9.15). Other vaccines

are made using inactivated forms of

natural toxins, such as the bacterial

toxin that causes tetanus.

Today many vaccines are made

with genetically engineered viruses

(Chapter 21). These harmless “transgenic” viruses incor-

porate genes from three or more different viruses in their

genetic material. After a

person is vaccinated with

an engineered virus, body

cells use the new genes

to produce antigens, and

immunity is established.

Examples are the “flu

shots” developed each year

to protect against influenza

viruses researchers iden-

tify as the major threats

during “flu season.”

antibodies provide “borrowed” immunity

People who are already infected with pathogens, such as

those that cause tetanus, measles, hepatitis B, and rabies,

Figure 9.15 Smallpox was eradicated by a global vaccination

effort. This girl survived smallpox, which can leave behind

heavily pitted scars. Vaccinations stopped in 1972 and the last

known naturally occuring case was recorded in 1977, in Somalia.

The image on the right shows smallpox virus particles. (Left: James

Hicks/Centers for Disease Control and Prevention; Right: Eye of Science/Science Source)

© Matt Meadows/Peter Arnold, Inc.

9.8

Vaccine Age of Vaccination

Hepatitis B Birth

Hepatitis B boosters 1–2 months and

6–18 months

Rotavirus 2, 4, and 6 months

DTP: Diphtheria, tetanus, and 2, 4, and 6 months

pertussis (whooping cough)

DTP boosters 15–18 months, 4–6 years,

and 11–12 years

HiB (Haemophilus influenzae) 2, 4, and 6 months

HiB booster 12–15 months

Pneumococcal 2, 4, and 6 months

Pneumococcal booster 12–15 months

Inactivated poliovirus 6–18 months

Inactivated poliovirus boosters 4–6 years

Influenza Yearly, 6 months to 18 years

MMR (measles, mumps, rubella) 12–18 months

MMR booster 4–6 years

Varicella (chicken pox) 12–18 months

Varicella booster 4–6 years

Hepatitis A series 1–4 years

HPV series 11–12 years

Meningococcal 11–12 years

Table 9.3 Recommended immunization

schedule for Children

Source: Centers for Disease Control (CDC), 2012

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