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David Crawford is a Clinical Nurse Specialist in the HIV/AIDS Unit St. Vincent's Hospital, Sydney. |
Red lights, green lights, amber lights. This was it, another attempt at explaining this new disease that had hit the headlines more than once in the last couple of months. Another dinner party where nobody could talk of anything else. Because I was the nurse, I tried to help the others understand what this disease did to the immune system. It was 1986, and a couple of my friends were sick. A lot more were scared, some terrified.
I jump into my latest model protein sportscar and go for a drive. This is no ordinary city, yet it should be familiar. The streets are tubular and branch off in all directions. Pulsing along the thoroughfares in a thick fluid are saucer-shaped vehicles, the red blood cells, called erythrocytes. They are the heavy transports in the system, working very hard to carry their precious cargo of oxygen to the billions of voracious inhabitants of the city. They also cart away waste carbon dioxide, which is exchanged for oxygen in the city's central ventilation system, the lungs. The laws of this city do not allow erythrocytes to work for longer than 120 days. Speeding along with the traffic, I pass a sign: "Welcome to Soma", a foreign body, as if it were an alien from outer space.
One of these cells turns on a green light in the immune system. It sets about telling its mates about this weird-looking creep who's trying to set up shop in town. Usually such creeps are bacteria, viruses, cancer cells, anything in fact that's not supposed to be around.
Garbage collectors are important in any city, and Soma is no exception. The street sweepers in Soma are called macrophages. Mac drives one of these vehicles, which he refers to affectionately as his macmobile. Mac and his machine spend most of the day cleaning up the crap and other garbage left around the city's streets. The macmobile gobbles up most things without much trouble. Broken-down cells, for instance, like the tired old erythrocytes that have just run out of puff after 120 days of service. Mac's machine doesn't mind knocking off creeps like bacteria and viruses, which are generally known as antigens in Soma. But before the macmobile deals with these unsavoury characters, Mac takes mug shots and sends them off to Helen. Helen is the roving inspector of Soma's immune system. Her job classification: Helper T cell.
Most of us have had experience of a virus at one time or another. The influenza virus is a perfect example of the many that exist: herpes is another that has become well known. So what is this virus that can only be seen by an electron microscope, and can make you so sick? A virus may contain either a strand of DNA (deoxyribonucleic acid) or RNA (ribonucleic acid) encapsulated in a protein coating.
Mac faxes the mug shots to Helen. He also issues an all-points bulletin over the radio channel Interleukin 1. All defence systems are now on alert as Soma's forces gather, waiting on instructions from Helen. Helen gets in contact with Bob. He is a B cell, a commander in Soma's defence system, and has been expecting to hear from her after receiving Mac's APB. Bob and Helen now meet with a large number of brothers and sisters from the T and B cell family to plan an attack on the invading antigen.
By now you're thinking, "Okay, what are RNA and DNA?" If you go to your kitchen cupboard and get out a jar, a tin, or just about anything that has been bought at the supermarket, somewhere on the product you will find a lot of lines of various thicknesses, side by side. This is the bar code. (Did you go to the cupboard?) Maybe you already know that the bar code carries a lot of information that is recognised by a scanner connected to the cash register, which is connected in turn to the store's central computer. Most importantly for us, the bar code tells the cash register operator the product's price. But as well as this, it also tells the store manager various other things about the product - the quantity sold, the number of items that will need to be reordered, and so on.
You have just discovered the most important thing about DNA and RNA. They are strands of information, like bar codes, but instead of lines, the bearers of information in RNA and DNA for chemicals.
A meeting to plan strategies takes place in a downtown office block, the Spleen Building. Smaller meetings are held in the out suburbs, in chain-stores called "Lymph Nodes". Bob and Helen and their family start crunching information about the antigen into their personal computers. While all this is happening, Helen remembers she has to contact another of her relatives, a real mean guy called Kelly. Kelly is a killer T cell, and the front-line hit man of Soma's defence forces. Helen soon reaches Kelly on radio channel Interleukin 2, and he begins to recruit and multiply his forces.
The bar code as it appears oil the jar looks pretty much like a strand of RNA. If you split it in two and twist each end in opposite directions to make a double spiral, or helix, you have DNA. So RNA and DNA can be thought of as bar codes which are found in every living cell. The information which RNA and DNA carry allows cells to produce proteins. Each individual cell contains a specific bar code to produce a specific protein. In a way, this is just like the bar code on products at the supermarket telling the computer that the item currently being charged is a jar of jam, and not a frozen pizza. For example, RNA and DNA in a muscle cell can only produce proteins that make muscles - muscle cells are basically muscle factories.
Kelly's specialty is chemical warfare. If any of the aliens have managed to escape being terminated by other members of Soma's defence forces, it is up to Kelly to seek them out in the cells they have invaded. He punches holes in the walls of affected cells with a lymphotoxin gun, and grabs hold of invading viruses, destroying them with the same gun. He also detonates lymphokine smokebombs in the area, which attract Mac and his mates to the site of the alien invasion. The euphoric effects of the lymphokine soon whips them into a phagocytic frenzy. As a further measure, Kelly fumigates the area with interferon, a chemical that both inhibits viral replication and gives him extra killing power.
A virus by itself is not a living cell. It's just a bar code in a fur coat, and as viruses aren't known to be particularly environmentally conscious, the fur is probably harp seal at that. In order to reproduce, the virus needs to use the reproductive capacity of cells. It does this by inserting its RNA or DNA into a host cell. Once inside, the virus commandeers the cell's reproductive system to create more of its own kind. The effect of this is like sticking the same bar code on all the products in a supermarket. The computer would tell the store manager that the only product being sold was strawberry jam, and soon the shop would be full of nothing but jam, particularly if the manager was totally reliant on the computer for reordering.
Like sharks whipped into a feeding frenzy by the taste of blood, Kelly and Mac annihilate the enemy. It is time to slow them down, to turn on the immune system's amber light. This is the job of Sam, a suppressor T cell. It is up to him to slow down the killing frenzy.
He negotiates with Mac and Kelly's union. Some members are offered early retirement, and others administrative desk jobs. In a couple of weeks, when the antigen has been completely snuffed out, Sam will hand out the gold watches and turn on the system's red light, and Soma's latest battle will have been fought and won.
Who could have predicted the havoc that was to be wreaked by a fragile, protein-coated strand of RNA which, outside the body, can be easily killed off with household bleach? This is the human immunodeficiency virus (HIV), the cause of the disease known as Acquired Immuno-deficiency Syndrome, or AIDS. Depending on your perspective, AIDS is either difficult or easy to catch. Infection is almost certain when HIV-contaminated fluid enters directly into the bloodstream. During sexual intercourse, for example, small tears may occur in the skin lining the sexual organs, giving the virus direct access into the bloodstream. Sharing syringes which are used intravenously provides another vector for entry. The AIDS virus, this tiny wisp of RNA, is obviously far more than just a virus. It has quickly become a political football and the cause of a social cataclysm.
Back at the Spleen Building, the information crunching has thrown up a detailed description of the invading antigen. Soma's defence forces want to remember this creep so that if he shows his face in town again, they can retaliate a lot faster. They enlist the help of a member of Helen's family - Martha, a memory T cell. Her job is to memorise the mug shot of the specific antigen, and to alert the immune system if it ever tries to return. The next time around, the response will be so swift that the creep won't know what's hit him.
Practising unsafe sex, as defined out by the AIDS council is like playing Russian Roulette and try these statistics "... the World Health Organisation estimates that for every person sick with AIDS there are 100 people carrying the disease - there have been 3368 cases of AIDS until 30 June 1992".
As I sit in my latest-model protein sportscar, I catch a glimpse of an official-looking woman in a finely tailored business suit. Her hair is pulled back into a tight bun, not a wisp out of place. As she approaches, she glances my way. I know my eyes are giving away the excitement I am feeling. My heart is pounding wildly within my chest. I manage to squeeze a nervous "hello" around the tightness in my throat. Without a word, she stares into my eyes as if spellbound, and I start to feel uneasy.
Seeing Ken at the beach made me go cold. Was it my imagination? "Great to see you. We must go horse-riding again soon" I said, as I walked away after a short chat. I'd seen the telltale signs many times before. Ken didn't need to tell me he had AIDS. I felt numb. This was the first of my friends to have contacted the disease. But now my clinical experience with it seemed so irrelevant.
"New in town?"
"Um.... yes." I must look more out of place than I thought. Or maybe she's
just observant.
"I've never seen a car like this before. A friend of mine, a guy called Mac,
told me you were new around here". She's nosey too, and this place is hot with
gossip.
"Like a ride?"
"Well, I shouldn't really. I'm still working, but well, okay". I breathe a sigh
of relief as we race along the freeway. A smug smile slowly spreads across my
face. This has been my easiest pick-up in a long time.
Later I visited Ken in the AIDS ward. Lying in the bed was a mere shell. This was the man that I used to go horse-riding with. The skin stretched over the bones of his face like an artist's canvas, so tight it seemed ready to split at any second. His bones grated as I hugged him. He managed to gasp out a muffled hello, but he was very drowsy due to massive doses of pain-killing morphine. I helped him to the toilet at his request. As I stood outside, for nearly 15 minutes, tears welled in my eyes as I listened to the gut-wrenching sounds of his diarrhoea. He was only 28 years old, and I knew he was dying. I didn't realise then that it was going to take two years.
The evidence of our passion is temporarily inscribed in the sand close by to where we sit. I am feeling that warm inner glow that comes from just having made love, even though I don't know the woman beside me. We're feeling free and easy, so who cares?
Once in the bloodstream, the AIDS virus is recognised as alien by the helper T cell. The T cell immediately attaches itself to the AIDS virus in an attempt to identify it. It is thought to be at this point that the virus injects its RNA into the T cell. But as we have seen, RNA is like a bar code for protein replication. What happens in the case of the AIDS virus is not much different from swapping bar codes over in a supermarket. The T cell becomes the factory for the manufacture of the AIDS virus, producing so many, in fact, that the T cell virtually destroys itself - very walls of the supermarket give way to strawberry jam.
"What's your name?" I ask her.
"Helen T cell. And yours?"
"Alistair... Alistair Aids."
Helen and I have embarked on an affair that Soma can do nothing about. Within 60 days Helen is pregnant, and I am going to be a father. This is the moment I have been waiting for - the destruction of Soma. But even in my triumph, my thoughts are already turning greedily to all the other cities this vulnerable little planet contains, particularly those which have listened eagerly to the moralists and think they are safe. I don't discriminate. just one moment of carelessness, and I shall have found my next love.
Why some people go on to develop AIDS and others don't is still a mystery. But anyone who has come into contact with the virus and become infected, even though they may have no signs or symptoms of the disease, can still pass the AIDS virus on. Even after initial infection, it may take up to 60 days before tests register positive and confirm the presence of the virus - this is the "window period". Protection from the virus means using the "safe" practice guidelines for your particular lifestyle.
They don't talk about me much at dinner parties any more. Sometimes I get the odd mention, like "By the way, did you hear about......?" "Hmmm, it was the big A." I guess I've become common and boring. But they still wonder who I will get next.
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