Human Immune System

IN JENNY'S DEFENSE
by Rick Destree, M.D.

I Am Fearfully and Wonderfully Made

Jenny's temperature is 100 degrees F. and she has been in bed most of the afternoon. Because she is such an enthusiastic eight-year-old, it is rare for Jenny to be without her friends on Saturday. Today, however, she doesn't feel like venturing outside her bedroom. She felt fine last night, but this morning she woke up with a sore throat worse than any she's ever had before.

Despite her misery, Jenny is comforted by all the attention she is receiving. She is glad that her parents are taking such good care of her. Deep down inside she realizes that I am taking care of her, too, even though we have never met. Little does she know that without me she could not even survive a common cold—not that I can take any credit. My wonderful Creator, the Lord Jesus Christ, placed me inside Jenny months before she was born to watch over her, day and night. You see, I am Jenny's immune system!

Actually I should say, "We are Jenny's immune system!" Like all the organs and tissues of her body, I am composed of billions of cells. I am unique, though, among her many organs because I am scattered throughout Jenny (unlike my friends, the heart and the eye, whose cells are gathered into one place). My cells roam tirelessly throughout her body looking for anything that could be wrong.

My best buddy, the stomach, once said that I reminded him of a collection of wild African animals. Innocently, I asked him which ones. He replied tersely, "Well, lots of them, don't you know?" He gets cranky at times. I would too if I had to digest the kind of food Jenny eats occasionally. Once she ate a peanut butter, mayonnaise, and pickle sandwich. Yuuucckk! That'd make anyone grumpy!

I've been working pretty hard the last couple of days and my gastric friend is wise to compare me to hunting animals. You could say that my cells have been on the prowl. Most of the time, however, I'm not sure exactly how we strange-looking creations work together to protect Jenny from infection. I do know that we are marvelously coordinated and that Jesus is in control of everything.

Here's what has been taking place inside Jenny over the past several days. Earlier this week Jenny came in contact with another girl who had a cold. Unfortunately for Jenny, some of the cold viruses from her friend decided to take up residence in Jenny's throat. Well, I'll tell you, Jesus knew what He was doing when He created me! As soon as those nasty viruses got inside Jenny I kicked into high gear. Without delay, I sent a slue of special blood cells called polys (PALL - lees) to deal with Mr. Cold Virus. My polys became like fast-moving cheetahs hunting their prey.

Unfortunately, by the time the polys got to Jenny's throat in sufficient numbers, the virus army had already invaded the cells of her nose and throat. White patches started developing on her tonsils.* These white spots are the graveyards of viruses and polys that have fallen in battle. I was able to contain the cold viruses to Jenny's throat, but I could not get rid of them all.

I was not deterred! God has given me an arsenal second to none, so I sent my mega-hunters to the scene, my macrophages (mack - row - fa - juz). Macrophages are like oversized hyenas—they're relentless and they will eat almost anything, dead or alive. In Jenny's bloodstream macrophages are called monocytes (MON - o - sights), and I like to refer to them as my roaming crocodiles. Any microbe that tries to get into Jenny's blood is history! Once the macrophages arrived at Jenny's throat they were able to clean up a lot of the mess. However, those virus guys were not ready to give up yet.

While the cheetah-like polys and scavenging macrophages were defending the territory, I decided to release special cells from their "cages" in Jenny's lymph nodes in order to help. Like hunting lions, special fighters called T-cells came to the rescue. This part of my immune system is so fierce people have dubbed them "killer cells." The abilities of each cell are actually a cross between the ferocity of a lion and the lethalness of a scorpion. Once the T-cells came in contact with her virus-infected cells they pounced on them. They grabbed the cells by the neck and held them down. (Cells don't really have necks, but you get the idea.) Next, the T-cells "injected" the infected cells with their deadly poison, killing them.

T-cells then released chemicals into Jenny's bloodstream, causing her body temperature to rise. Many people see fever as bad, but small elevations in temperature slow down the invading viruses and make the cells of my immune system more efficient in fighting foreign microbes.

While the T-cells were fighting, their sibling B-cells were back in the lymph node dens cooking up a surprise attack. B-cells are one-of-a-kind creations that produce something called antibodies. Actually, B-cells must mature and become plasma cells in order to make antibodies. Antibodies are skillfully crafted protein molecules Jesus invented to help people fight off infections, whether they're caused by bacteria, viruses, fungi, or parasites.

Once released, antibodies react to an invading virus like an ant colony responds to a trespassing insect. Just as ants recognize a locust invading their home territory, antibodies identify the foreign virus and attack it without hesitation. They attach themselves to the virus and thus prevent it from entering one of Jenny's cells.

Antibodies also tag the infected cells, making them easier for my macrophages and T-cells to find. Other molecules circulating in Jenny's blood called complement proteins combine with antibodies to make the damaged cells more "appetizing." Macrophages find these antibody- and complement-coated cells more "tasty" as a result. It's kind of like adding salt and pepper to food.

Ironically, most of the unpleasant cold symptoms that Jenny is experiencing are the result of my trying to fight her cold; they are not caused by the virus itself. In a couple of days Jenny will be feeling much better and will be eating normally again. Although this is a great relief to most of my friends and me, the stomach is enjoying his vacation. He became cranky upon hearing the news that he would be going back to work soon. "You guys have never had to digest marshmallows early in the morning!" he protested. He had a point...

To me, Jenny's body is like a pristine wilderness which Jesus has given me to protect. I'd guess that most of you didn't know that God did so much to keep people healthy and safe. I truly reflect the love and the concern the Heavenly Father has for His people. Although my cells are scattered throughout the body and not neatly packaged like other tissues, God ingeniously coordinates all my skills to provide ultimate protection. The Lord Jesus, my Creator, is the Great Protector of us all—large and small. He can be trusted!