Our Defense SystemOur Defense System

Spring 2013Spring 2013

Two ways your body defends you

• Nonspecific – attacks invaders without discretion. (doesn’t attack only specific invaders)

• Specific – cells that are trained to only attack one kind of invader (chicken pox, for example).

Non Specific DefensesNon Specific DefensesFirst line of defense (4)First line of defense (4)

1.1. SkinSkin– Physical barrier as long as it’s Physical barrier as long as it’s

unbrokenunbroken– Chemical barrier – sweat Chemical barrier – sweat

• acidic - inhibits bacterial growthacidic - inhibits bacterial growth• contains lysozyme - an enzyme that contains lysozyme - an enzyme that

digests bacterial cell walls (also in digests bacterial cell walls (also in tears)tears)

Non Specific DefensesNon Specific DefensesFirst line of defenseFirst line of defense

2.2.Hair – Hair – Some are large, like Some are large, like eyelashes or eyebrowseyelashes or eyebrows

Most are very small, Most are very small, called cilia, they line called cilia, they line the respiratory the respiratory system. They trap system. They trap and sweep particles and sweep particles out out

Nonspecific DefensesFirst line of defense

• 3. Mucous Membranes

– Layers of cells that produce mucous.

– Trap pathogens

Non specific DefensesFirst line of defense

4. Stomach Acid• Hydrochloric acid

(HCl) • pH around 1 or 2• Destroys most

pathogens you swallow• Stomach protects itself

with a thick lining of mucous

Non specific DefensesSecond Line of defense (4)

1. Inflammatory Response

2. Temperature response

3. Proteins4. White blood

cells

Inflammatory response – triggered by pathogens enter the skin

• Injured cells release histamine.

• Histamine causes local blood vessels to dilate, increasing blood flow in the area.

• But it also brings more white blood cells which will destroy the pathogens

• Increased blood flow causes swelling, redness, raised temperature.

Temperature Response

Normal body temperature is 37 degrees C (98.6 degrees F)

As pathogens invade, the body will increase

several degrees. This will inhibit disease-causing bacteria.

Proteins and White blood cells• When a cell is attacked by a virus, the cell

releases a protein called interferon

• Interferon travels to other cells and prevents the virus from successfully reproducing

• White blood cells travel throughout the body and destroy and consume any non-self cell.

Specific ResponseCertain white blood cells (T cells) are

programmed to recognize only a particular pathogen (Called antigen)

You have thousands of different T cells. They each recognize a different antigen.

When they recognize an antigen, they clone themselves many times and will destroy the antigen. Some stick around for years and work as immunological memory

Example: Chicken Pox• 1st grade, 1975, San Antonio, Tx. Peter

Knickerbocker (not making that name up…) contracted chicken pox from an unknown source.

• The virus began to attack his skin cells, but it takes a week or so (called an incubation period) before there was a noticeable problem…fever, pox marks, etc.

• During that incubation period, he sat next in the desk next to me.

Example: Chicken Pox• I contracted Chicken pox from him and my

body had never seen it before. The first and second line of defense went to work, but the virus reproduced faster than the nonspecific response could control it.

• A white blood cell consumed one of the virus particles.

• When it consumed it, it blew a whistle by sending out a signal (chemical: interlukin)

Example: Chicken Pox• T cells arrive at the scene of infection. I

have thousands of them but they are all different. One of them matches the chicken pox virus’ protein coat.

• Before a match is found, time passes and many more viruses replicate. I’m feeling pretty miserable during this time…stupid Peter Knickerbocker!!

• When a match is found, the T-cell rapidly clones itself to make many, many, many duplicates

Example: Chicken Pox• The chicken pox T cell clones all destroy

the virus cells resulting in my feeling much better

• Some chicken pox T cells will stick around for a long time (they are still there!!). They are called memory cells

• When I go back to school a week or so later, Drewann Kittlitz (not making that one up either) has gotten chicken pox (probably from me) and spreads it back to me

Example: Chicken Pox• My body immediately recognizes the virus

and the memory cells rapidly divide and attack. I never even knew I had caught it again.

• This is why you can have the flu and not catch the flu from your own toothbrush a week later.

• It’s all about the memory cells.

Primary and secondary response• Let’s graph it!!• Vaccines introduced a deadened form of a

pathogen. Your body makes the memory cells

• Then when you are exposed to the real thing, your body knows exactly how to fight it.

• A vaccine is like a fire drill for your immune system

What’s on the test

• Viruses vs. bacteria (flip chart)

• HIV/AIDS virus notes

• Pathogen chart…this portion (Only (Only this portion)this portion) is open note)

• Your defense system notes