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The Immune System

Let’s begin with three mysteries.

Mystery #1 - Smallpox was a disease which caused pus-filled blisters to form on people’s bodies. The blisters would fall off and leave scars; about a third of all people who contracted smallpox would die from organ failure. (The last known case of smallpox was observed in the 1970’s; smallpox has now been eradicated.) People who survived smallpox never got it again. You could not get smallpox twice.

Milkmaids who worked with cows often got the milder disease called cowpox.

Mysteriously, these milkmaids never seemed to contract smallpox.

“In May 1796, English Biologist Edward Jenner found a young dairymaid, Sarah Nelms, who had fresh cowpox lesions on her hands and arms. On May 14, 1796, using matter from Nelms’ lesions, he inoculated an 8-year-old boy, James Phipps. Subsequently, the boy developed mild fever and discomfort in the armpits. Nine days after the procedure he felt cold and had lost his appetite, but on the next day he was much better. In July 1796, Jenner inoculated the boy again, this time with matter from a fresh smallpox lesion. No disease developed, and Jenner concluded that protection was complete.” (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1200696/).

Jenner’s experiment is famous, but it was certainly not the first time this practice had been tried. Many cultures had for centuries been inoculating people by taking the pus from smallpox pustules and injecting it under the skin of people who hadn’t had smallpox. 97% of these inoculated people survived.

But why? What was going on?

Mystery #2 – Blood transfusions

Before the 20th century, transfusing blood to someone who had lost a lot of their own blood was rare. Why? If someone lost a great deal of blood, doctors might try to give them blood from other humans, or even from animals like sheep. Sometimes the recipients did just fine…but often they developed chills, fever, pain, shortness of breath…and occasionally they would die.

But why? What was going on?

Mystery # 3 – The second baby

Occasionally, the following scenario would occur: A woman would give birth to a perfectly healthy first baby. But when she gave birth to her second baby, the child would develop jaundice, a yellowing of the eyes (and skin, in light-skinned babies) and anemia (a lack of sufficient blood cells). Unfortunately, these babies often died.

But why? What was going on?

The answer to all three mysteries lies in understanding…The Immune System

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1200696/figure/F5/

bidflubook.com

historyspace.blogspot.com

www.antiqueszone.co.uk

http://newsatjama.jama.com/2012/02/13/tapeworm-infection-prevalent-in-refugees-may-trigger-seizures/

What’s the purpose of our Immune System?

Who’s trying to get in…and why?

Where are they most likely to get in?

And how?

And which are harmless? And which are lethal?

Let’s get a sense of their size by looking at the Scale of the Universe website.

The First Line of Defense – Barriers and Mechanisms

Our body has some very basic defense mechanisms to keep microbes from invading us. List those that you can think of.

Anatomical Structures / Mechanisms and Actions

The Second Line of Defense - Inflammation

Sometimes the first line of defense is broken by the invaders and they “set up shop” inside our bodies and start to reproduce. One of our body’s primary defense mechanisms at this point is something called an inflammation, or an inflammatory response which fights the invaders. We’ll meet the players and learn lots of details shortly, but you may already be very familiar with aspects of an inflammation response.

When a part of the body experiences an inflammation, the condition is often described as a “something-itis”, where the “something” is the part of the body that is inflamed. And since the Respiratory System is so vulnerable, that’s where a lot of “-itis”es occur.

So, for example, if you have an inflammation in your bronchi, it’s called ______.

Your tonsils are some lymph glands (which house a special kind of infection fighter called a lymphocyte (more later)) located near the pharynx. If your tonsils become inflamed you have ______

If an infection causes inflammation around your larynx, you have ______.

If an inflammation in your nasal cavity causes pressure on your sinuses, or an infection migrates into your sinuses themselves, you officially have ______.

One kind of Pharyngitis is inflammation resulting from a bacterium called Streptococcus pyogenes. This is simply a fancy name for ______.

What do we typically call an inflammation response in the bronchioles of the lungs? (This is a “trick” question.)

What other “-itis”es can you think of that are NOT connected with your respiratory system?

The cells involved in an inflammation response, who rush to defend you from invaders, reside in several places. Some live in your bloodstream, and some live in Lymph Tissues. Let’s see the Lymph system on the Visible Body. Then we’ll see a slide show about blood cell types.

In the next activity we’ll act out the specifics of an inflammatory response and probe further into the immune system.