Issue date: Jan 9, 2000

In this report:
How your body fights attack
Why your nose runs
Your body's best line of defense
Dr. Mitchell explains the immune system
8 steps to peak immunity
Don't show for work when sick!
Quiz: Cold and flu facts
Checklist: Cold or flu?
The future of colds
Garlic, yogurt and chicken soup for wellness
About Dr. Mitchell

How your immune system works

magine your body is a fort under attack from viruses and bacteria. You have two lines of defense. First, your skin and the mucous membranes in your respiratory tract literally screen out germs. If these lines of defense are penetrated, the immune system kicks in, sending white blood cells to the affected region. Backup troops -- specialized white blood cells, proteins in the blood known as antibodies and other blood components -- follow, working in an orchestrated effort to strike down the invaders.

1 The attackers
Viruses and bacteria need an entry portal, such as irritation or dryness in the mucous membranes or an opening in the skin. Normally, mucous membranes contain immunoglobulin A, which kills off invaders. If there is an entry portal, or a particularly large load of virus or bacteria (someone with a cold sneezes in your face), invaders can break through the barriers.

How fever begins:
White blood cells release endogenous pyrogens that work on the hypothalamus to raise your temperature. Most viruses and bacteria can't thrive in hot environments. Some doctors suggest NOT taking fever reducers unless your temp is very high -- say, over 101 degrees.

2 The defenders
Antibodies in the blood recognize the invaders as foreign. A chain reaction then occurs that causes white blood cells stored in the blood vessels, spleen and bone marrow to rush to the point of entry.

3 THE "KILL"
At the entry point, white blood cells literally swallow the invaders, releasing powerful substances to destroy them.

Go to the top

WHY YOUR NOSE RUNS

When an organism invades, the body has an inflammatory response. It starts producing more mucus (containing antibodies) for a thicker layer of protection (that's why your head, throat and chest are congested). Phlegm is just a mass of mucus mixed with dead white blood cells. Clear or slightly yellow phlegm usually means the invaders have not penetrated deeply. But green or brown phlegm means more dead white cells, indicating that the organisms may have caused more damage. See a doctor.

Go to the top

YOUR BODY'S BEST DEFENDERS

TONSILS. Collections of lymph tissue in the back of the throat filter out organisms that cause infection.		THYMUS. Organ in which new white blood cells grow up, developing specialized functions.
LIVER. White blood cells in this "filter" organ remove organisms from the blood as it passes through.		SPLEEN. Removes abnormal cells from circulation.
MUCOUS MEMBRANES in the respiratory and gastrointestinal tracts repel organisms and allergens and contain immunoglobulins that battle organisms that try to penetrate.		LYMPH NODES. Act as "filters" and produce antibodies to destroy invading organisms or abnormal cells.
BONE MARROW. All immune-system cells start out here. White blood cells (neutrophils, lymphocytes) are formed, then released into circulation.		SKIN: Keeps organisms and allergens from entering the body.

Go to the top