defend you as you age?
Elementary schools are breeding grounds
for the common cold. Kids pass their
germs around as often as they share
their lunch. For children, catching a cold
may not be a big deal. They might take it
easy for a few days while their immune
system kicks into action and fights off
infection. But for their older teachers and
grandparents, each cold can be more of
a challenge. It may take a week or longer
to get back to feeling 100 percent. Does
that mean that the immune system gets
weaker as we age? That’s what
gerontologists are trying to figure out.
Our immune system is a complicated network
of cells, tissues, and organs to keep us healthy
and fight off disease and infection. The immune
system is composed of two major parts: the
innate immune system and the adaptive immune
system. Both change as people get older. Studies to
better understand these changes may lead to ways
of supporting the aging immune system.
BIOLOGY OF AGING: RESEARCH TODAY FOR A HEALTHIER TOMORROW 31
Innate immunity is our first line of
problem—may help gerontologists find ways
defense. It is made up of barriers and certain
to temper its associated diseases.
cells that keep harmful germs from entering
The adaptive immune system is more
the body. These include our skin, the cough
complex than the innate immune system
reflex, mucous membranes, and stomach
and includes the thymus, spleen, tonsils, bone
acid. If germs are able to pass these physical
marrow, circulatory system, and lymphatic
barriers, they encounter a second line of
system. These different parts of the body
innate defense, composed of specialized cells
work together to produce, store, and transport
that alert the body of the impending danger.
specific types of cells and substances to combat
Research has shown that, with age, innate
health threats. T cells, a type of white blood
immune cells lose some of their ability to
cell (called lymphocytes) that fights invading
communicate with each other. This makes
bacteria, viruses, and other foreign cells, are
it difficult for the cells to react adequately to
of particular interest to gerontologists.
potentially harmful germs called pathogens,
T cells attack infected or damaged cells
including viruses and bacteria.
directly or produce powerful chemicals that
Inflammation is an important part of
mobilize an army of other immune system
our innate immune system. In a young
substances and cells. Before a T cell gets
person, bouts of inflammation are vital
programmed to recognize a specific harmful
for fighting off disease. But as people age,
germ, it is in a “naïve” state. After a T cell is
they tend to have mild, chronic inflamma-
assigned to fight off a particular infection, it
tion, which is associated with an increased
becomes a “memory” cell. Because these cells
risk for heart disease, arthritis, frailty,
remember how to resist a specific germ, they
type 2 diabetes, physical disability, and
help you fight a second round of infection
dementia, among other problems. Research-
faster and more effectively. Memory T cells
ers have yet to determine whether inflam-
remain in your system for many decades.
mation leads to disease, disease leads to
A healthy young person’s body is like a
inflammation, or if both scenarios are true.
T cell producing engine, able to fight off
Interestingly, centenarians and other people infections and building a lifetime storehouse who have grown old in relatively good health of memory T cells. With age, however, people generally have less inflammation and a
produce fewer naïve T cells, which makes
more efficient recovery from infection and
them less able to combat new health threats.
inflammation when compared to people
This also makes older people less responsive
who are unhealthy or have average health.
to vaccines, because vaccines generally
Understanding the underlying causes of
require naïve T cells to produce a protective
chronic inflammation in older individuals— immune response. One exception is the shingles and why some older people do not have this
vaccine. Since shingles is the reactivation
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IMMUNE SYSTEM