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by
Jacqueline Jaeger Houtman
“No, a mosquito,” giggled another of the creatures.
Dorothy scratched Toto behind the ears and remarked “I don’t think we're in our definitive host anymore! But
who are these curious creatures?”
“They call us munchkins,” one of them replied, “because we're phagocytes and we MUNCH intruders... like you!”
With that, they leapt at her. Dorothy screamed, and, in a puff of smoke, the munchkins scattered. In their place
was a strange-looking woman in an old prom gown.
“Who are you?” asked Dorothy.
“I’m Glinda, the Good Witch of Immune Evasion,” she replied, “and I’m here to help you.”
“What can you do for me?” asked Dorothy.
“Well, you may have heard of my cousin, the Wicked Witch of Immune Surveillance.” explained Glinda. “She will
do everything she can to kill you, but I can provide you with the means to stay away from her. Here.” Glinda
gave Dorothy a red jacket. “It’s an erythrocyte; you can hide in here.”
Dorothy was disappointed. “What, no ruby slippers?”
“Red shoes, red blood cells, what's the difference? Now what would you like to do?”
“I’d like to reproduce.”
“I'm afraid you'll have to do that asexually. This is your intermediate host.”
“Oh, that just won't do. How can I undergo sexual reproduction?”
Glinda thought about that question for a moment. “You'll have to get back to your definitive host,” she said.
“Maybe the Wizard can help you.”
“The Wizard of Oz?”
“No, the Wizard of Pathogenesis.”
“How do I find him?”
“You just follow the...”
“I know, the yellow brick road.”
“No, you follow the blood stream.” and Glinda began to sing. “Spread hematogenously, spread
hematogenously...” The munchkins joined in as Dorothy and Toto made their way along the nearest blood vessel.
Dorothy was making good progress until she came to a bifurcation. “Which way do I go now?” she wondered
aloud.
“Well, you could take the radial artery,” came a voice from nowhere.
Dorothy nearly jumped out of her cell membrane. “Who said that?”
She heard it again. This time it said, “Or you could take the ulnar artery.”
Dorothy turned around, and there it was: A not-very-scary Scary Coli, with flagellae sticking out all over, like bits
of straw. “Excuse me for being so startled, she said. “I didn't see you there.”
“That's my problem,” he said forlornly. “Nobody even knows I'm here. I might just as well be natural flora. What I
really need is a toxin!” Now Scary was getting excited. “Shiga toxin, shiga-like toxin, enterotoxins, neurotoxins,
heat-labile toxins, heat-stable toxins, hemolysins, or ...dare I ask... an ADP-ribosylating toxin! Then I'd be a real
bacterial pathogen!”
Dorothy checked her pockets and her little wicker basket. “I don't seem to have any toxins with me. But I'm
going to see the Wizard of Pathogenesis. Maybe he can help you, too.”
Scary’s eyes opened wide. “Can he give me a toxin?” he asked.
“I'm hoping he can help me to reproduce sexually,” replied Dorothy.
“I guess it's worth a try. How do we find this Wizard?”
Dorothy broke into song. “Spread hematogenously, spread hematogenously...”
After traveling a little while, Dorothy and Scary came across Tin Fluenza, sitting dejectedly in the middle of the
road. He did not move, and they weren’t sure if he was alive, until a muffled sound emanated from him.
“Drrr..Prrrt.”
“What is he saying,” asked Dorothy.
“Drr..Prrt.”
“It sounds like ‘oil can’ to me,” said Scary.
“Oil can?” wondered Dorothy.
Tin had finally had enough “NO!!” he cried. “DI particle, you dimwits!!!”
Dorothy and Scary were taken aback. “You can talk,” said Scary.
“Of course I can talk,” said Tin. “I just can't replicate.”
“I know how you feel,” said Dorothy sympathetically. “Are you stuck in your intermediate host, too?”
“No, I'm...defective,” said Tin, meekly.
“Scary and Dorothy exchanged looks. “How do you mean?” asked Scary.
“Pound on my chest,” said Tin. And Scary did just that. The sound reverberated for a few seconds.
“What an echovirus!” exclaimed Scary.
“That's the problem,” sighed Tin. “I'm just an empty capsid. I've got an incomplete genome.”
Dorothy and Scary conferred for a moment. Then Dorothy said “We're on our way to see the Wizard of
Pathogenesis. Would you like to come with us?”
“Sure,” said Tin, “but what can he do for me?”
“I'm going to ask him for a toxin,” said Scary, “preferably an ADP-ribosylating toxin.”
“And I'm going to ask him if he can help me get back to my definitive host,” said Dorothy.
“Can he find my missing genes?” asked Tin.
“It's worth a try,” said Scary, and the three would-be pathogens continued on their way, singing, “Spread
hematogenously...”
After a while, our heroes got the strange feeling that they were not alone. “I get the feeling we're not alone,”
said Tin, strangely.
“I think there's a fungus among us.” deduced Scary. This was confirmed when from behind came an unconvincing
“boo.”
Our three travelers turned calmly around. “Who are you?” asked Tin.
“My name is Candida albicans,” said the cowardly fungus, “but you can call me Candy Lion.”
“So you're the fungus,” said Scary. “Big deal.”
“To be more precise,” corrected Candy, “I'm a budding yeast!”
“So what?” asked Dorothy.
Tin yawned. “Yeah, who cares?”
“You see,” whined Candy, “that’s my problem. Nobody takes me seriously.”
“We all have our problems,” said Scary. “I'm atoxigenic.”
“I'm defective,” said Tin.
“I'm asexual,” said Dorothy.
And with that, our four pathogens sang (to a strangely familiar tune):
We could cause some inflammation
And lots of exudation
Necrosis of the spleen
Impetigo, a coma or perhaps a granuloma
If we only had the gene.
We could cause some pneumonitis
And pyelonephritis
Edema and gangrene
We could cause diarrhea and be really glad to see ya
If we only had the gene.
“Why don’t you come with us to see the Wizard of Pathogenesis?” suggested Dorothy. “Maybe he can help you.”
“How do we get there?” asked Candy. And they all sang: “Spread hematogenously...”
Little did our pathogen heroes know that they were being watched. “Ooh, those pesky intruders!” cried the
Wicked Witch of Immune Surveillance. “I've got to get them out of here.” She ordered her monkeys into action.
“I want you to do away with those four interlopers!”
“Yes, your ruthlessness,” groveled the monkeys, and they flew off to intercept our intrepid microbes.
As the monkeys approached, Dorothy cowered. “What are they?”
“They look like flying cytotoxic monkeys!” said Scary.
“Oh, no,” cried Candy, “what will we do?”
As they began to panic, Tin remembered something. “Wait a minute! Do you see any antigen-presenting cells
around?”
Scary began to catch on. “Oh, I get it. We're not being presented, so they can’t see us!” Everyone relaxed as the
monkeys flew right by, oblivious.
The witch tried another strategy. “Goblins!” she commanded. “Get them!”
The four travelers froze as they saw what was approaching. “Immunogoblins!” cried Tin. “We’re doomed.”
“What will we do?” asked Candy.
Then it was Dorothy’s turn to remember. “Immunogoblins recognize conformational epitopes.”
“Quick!” said Scary. “Antigenic variation!” With that, our heroes contorted themselves into unrecognizable
shapes and the immunogoblins went harmlessly by.
“AAAGH!” screamed the witch, fed up with her inept lackeys. “Do I have to do everything myself?” She
approached our heroes and said menacingly, “That's a lovely outfit you're wearing!”
The four looked at each other and shrugged their shoulders.
“I really enjoyed your seminar!” continued the witch.
“What is she doing?” whispered Candy.
“Great haircut!” said the witch.
“Hold it!“ cried Scary, approaching the witch. “What do you think you're doing?”
“I’m attacking you with one of the most powerful weapons in my immune arsenal,” she replied. “Compliments!”
“I think you mean complement,” groaned Candy.
“Oh,” said the witch meekly. “Never mind.” And she left.
After wandering about some more, our pathogens encountered a fellow in a tie-dyed lab coat and fluorescent
safety glasses. “It’s the Wizard!” they cried in unison.
“Yeah, yeah, so what can I do for you?” asked the Wizard, gruffly.
Scary was the first to speak up. “Glinda, the Good Witch of Immune Evasion sent us. She told us you could help
us. You see,” he admitted, sheepishly, “I'm atoxigenic.”
“And I'm defective,” said Tin.
“And I'm asexual,” said Dorothy.
“And I'm a wimp,” said Candy.
The Wizard took pity on this pathetic group and looked into his bag of microbiological tricks. “Here,” he said as
he handed Tin an icosahedral figure. “All you need is a helper virus. A little recombination and you're all set.”
“Oh, thank you,” exclaimed Tin.
“And you,” said the Wizard, indicating Scary. “I've got something for you, too.” He produced what looked to be
a loop of string.
“What is it?” asked Scary.
“It's a virulence plasmid,” explained the Wizard. “It has all the toxins you'll ever need. I threw in some antibiotic
resistance, too. No charge.”
“What about me?” asked Candy.
“You don't need anything,” said the Wizard. “You see, you're not a wimp, you're an opportunist. All you need to
do is wait, and when your host becomes compromised, you’ll be as feared as any primary pathogen.”
“I knew it all along,” said Candy, with a superior air.
“I don't suppose you've got anything in there for me,” said Dorothy, dejectedly.
“Well, no,” admitted the Wizard. “In order to get you back to your definitive host, we would need to go where
anopheles mosquitoes are endemic.”
“Kansas?” suggested Dorothy.
“No, a little farther south,” said the Wizard. “I have a hot air balloon, but it’s in the shop.”
“Rats!” complained Dorothy. “Now I’ll never get to reproduce sexually!” She was getting a little frustrated.
“Hold on!” cried the Wizard. “I think there’s a way. I saw it in a movie. Click your heels together and say ‘There’
s no place like host’.”
“I’ll try anything once,” said Dorothy. She did as she was told, but nothing happened.
“I think you have to keep trying,” suggested the Wizard.
So Dorothy tried again and again. “There’s no place like host. There’s no place like host. There’s no place like
host. There’s no place like host.” She started to get a little dizzy, then a lot. The world started spinning and
spinning...
“Judy, Judy, can you hear me?”
Judy opened her eyes and there was her mom, with a glass of juice. “You had me a little scared there. Are you
feeling better?”
“Oh, Mom, I had the strangest dream,” said Judy. “There were bacteria and viruses and fungi, and there was
this malaria parasite, and all she wanted to do was...”
“We all have strange dreams when we have a fever, now drink up.”
“But it seemed so real,” muttered Judy as she took a sip of her juice. She stopped as she became aware of a
faint buzz. It got louder, until it became a persistent drone. It was a mosquito.
Judy smiled. “Atta girl, Dorothy!”