A Waking Nightmare
Caitlin sees the haunting image over and over in her dreams. Anika, her eight year old patient from rural India, who is paralyzed from polio, is falling backwards. The girl’s doe-like eyes widen with terror. Her limp arms whirl like a windmill as she tumbles. Caitlin reaches out to help, but to her horror, she realizes that her own left arm is frozen at her side, as useless as Anika’s.
Caitlin jerks awake. The nightmare seemed so real. In fact, though she is awake now, it still seems real. Her left arm is indeed burning with a pins and needles sensation. Her hand does not feel like it even belongs to her, and it is clumsy and weak.
With growing panic Caitlin checks her grip strength repeatedly. Does she have polio? Sweat pours off of her. She feels nauseated. Her heart pounds in her ears, a thumping that mixes with the pulse of morning traffic outside.
Too Late?
The immune cells in Caitlin’s intestines have been working overtime for weeks, sorting through countless microbes that are as foreign to her privileged immune system as the foods and languages of India are to her suburban American senses.
Blending in among the harmless legions of germs in Caitlin’s small intestines is an international terrorist. As microbes swarm at the border, some polio viruses slip past the epithelial boundary and into Caitlin’s bloodstream. They are on a devastating mission. And now that they have gained access to the superhighways of her body and are speeding toward her spinal cord, how can they possibly be stopped? Her immune system has been caught napping. What can it do in response?
Playing Catch Up
In Caitlin’s terminal ileum (an immune hotbed at the end of the small intestines), a kind of white blood cell called a dendritic cell is stationed like a guard on duty. The cell swallows something tiny that it does not recognize. It is one of the viruses.
The dendritic cell wriggles its way through a lymphatic channel, like a private navigating the trenches on the front line, and slithers into a lymph node, the local command center. The cell touches a receptor on another white blood cell, known as a T cell. After this molecular salute, the dendritic cell presents the digested pieces of the polio virus to the T cell, like a border guard showing a strange passport to a superior officer.
The T cell studies the viral fragments. Caitlin has never before been exposed to polio, so this is a completely novel threat. The T cell cannot possibly appreciate what it is up against or respond in time. Or can it? Incredibly, instead of dithering, the T cell does something unexpected. It shouts an order: “Attack!”
At once this command rouses the full force of all branches of the immune system to join the battle. A mighty, but minute, army springs into action throughout Caitlin’s entire body.
The offensive is intense, but brief. During the whole battle, T cells maintain a missile lock on the polio viruses. B cells, already armed for this moment, churn out antibodies, like smart weapons that rain down death on the viruses by specifically targeting only them and nothing else in the body. Fired up and guided by chemical orders, the soldiers of the immune system quickly hunt down and dispatch all the polio viruses.
As Caitlin’s arm begins to wake up and regain strength (for it was simply asleep from her lying on it in her exhaustion*), she trembles with fatigue and relief. The last virus is eradicated from her system.
Viral Veterans
How were the B cells, the anti-aircraft guns of the cellular corps, already loaded with ammo specifically configured to target the polio virus? Normally it takes days to weeks for the body to devise such smart weapons.
Most puzzling of all, how did the T cell “know” how to respond to the threat? These cells are exposed to countless foreign substances every day, and they don’t sound the alarm. How could these microscopic marines already be so familiar with this foe and vanquish it so quickly?
It turns out that this particular T cell, like some crusty old military historian, has specialized in polio, studying its foe and keeping constant vigil against a potential polio infection. That has been its life’s work. But how can you prepare a detailed battle plan against a foe you have never even met? How can a cell remember something it has never encountered before?
The answer is vaccination. Caitlin is immune to polio not because of a natural exposure to the virus, but because she received the polio vaccine as a little girl.
How do vaccines do their job?
A Fortunate Discovery
Imagine that a peaceful nation (I will call it “Harmonia”) fears an aerial assault by a hostile neighbor. Fortuitously, before the outset of war, an enemy plane crashes on a spy mission, and Harmonia’s military recovers it nearly intact.
Seizing the opportunity to prevent an invasion, the military strategists in Harmonia analyze the downed craft to bolster their air defenses.
- Military planners design sophisticated smart missiles that can lock onto the aircraft heat signature and radar pattern.
- Intelligent surveillance systems are put in place that recognize the enemy insignia and send out instant alerts.
- Ground spotters are trained to recognize the distinct hallmarks and silhouettes of the potential attackers.
- Fighter pilots engage in simulated dogfights against planes which imitate the appearance, tactics, and the capabilities of their potential foe.
- Anti-aircraft gunners drill repeatedly against drones made to look and act as much like the enemy aircraft as possible.
- Military strategists even derive the flight path of a possible sneak attack from the site of the crash, so they know where to look.
- Communication systems in key areas are strengthened.
Rude Welcome
When the long-feared invasion does take place, rather than being taken by surprise by unfamiliar aircraft with unknown capabilities suddenly appearing overhead, the air defense system of Harmonia is ready.
- Radar analysts do not puzzle over confusing bogeys on their screens. They immediately recognize their foe and sound the alarm.
- Thoroughly drilled spotters easily track the aircraft.
- Anti-aircraft gunners fire confidently. They know they can hit the planes. They have already done it over and over in their simulations.
- Fighter pilots turn the tables on the sneak attackers by anticipating their every move and shooting them out of the sky.
The invasion is foiled. Harmonia is saved.
War Games
Vaccinations act like simulated infections which train the immune system and prepare it for actual infections in the future. Vaccines are merely war games.
Caitlin has been saved from the fate of paralysis or death because of a training simulation at age two months that taught her body how to fight against polio virus without the risk of acquiring the infection.
As I use this metaphor of military planning and technology, you may be thinking that I am about to extol the brilliant vaccine specialists who devise all the ways in which our bodies can prepare for infections and prevent them. But vaccine specialists do not design any of the smart weapons, warning systems, and immune responses that prevent devastating infections like polio. No, in this analogy the real genius behind immunity is not the scientist who develops the vaccine. It is the immune system itself.
All a vaccine does is to crash a germ harmlessly onto the native soil of your body. Your magnificent immune system does the rest. It develops the weapons, warning systems, and plans to keep you safe.
The real trick to developing and implementing vaccination is figuring out how to crash the germ in your body without hurting you too much or destroying the useful information during the crash.
In the next post, part 3, I will explore how the COVID-19 vaccines do that.
Dr. Bill Maynard
*Lest you think Caitlin’s false crisis is simply a cheap literary device to heighten suspense, I based this story on a true account from the great physician, Dr. Paul Brand. In Ten Fingers for God he describes an event in which his heel went numb from prolonged sitting during a train ride, and he assumed that he had contracted leprosy from his long work with those suffering from Hansen’s disease. It was described as “the blackest moment of his whole life.”