Your immune army uses an amazing array of weapons to protect you from cancer and microbes.
There are good guys (our white blood cells) and bad guys (cancer and microorganisms) in us, and they are fighting it out for control of the territory that is you. I am going to put you in front of a very powerful microscope so you can see—in vivid detail—this constant vicious struggle going on inside every one of us. The opposing armies conduct complex military maneuvers and deploy a fantastic and unimaginably small array of war machinery, all coordinated by a sophisticated communications system.
The bad guys—the foreign invaders—are constantly attacking us; I speak of allergens, infectious agents, various toxins, and cancer. Our immune army, our guardian, is comprised of dozens of cell types with hundreds of different functions. In any single person, immune cells number in the hundreds of billions—several times more then the number of stars in our galaxy or galaxies in our universe! They routinely sacrifice their teeny (but incredibly complex) lives to defend us.
Healthy immune cells are essential to our survival in this ongoing war, and they are relentless in their pursuit of cancer and other foreign invaders. When activated, they make Hitler, Stalin, and Mao look like neighborhood bullies. Immune cells attack in extremely large numbers—far larger than any army ever. Come to think of it, every single human has far more immune warriors than all the armies in history put together. Their onslaught is superbly coordinated by an extremely sophisticated communication and command system; human military intelligence operations are kindergarten games in comparison. Using a complex language comprised of molecular words (proteins, glycoproteins, cytokines, cell-signaling molecules, neurotransmitters, etc.), your immune cell soldiers release a barrage of chemical messages that identify foreign invaders, provide their location, estimate numbers, and coordinate the attack.
Macrophage engulfs and phagocytizes a cancer cell. From “The Immune System” published by The Upjohn Company.
And what an awesome attack! Our immune cells sport an arsenal that would make Star Wars look puny. Immune cells can blow up enemy invaders. They can shoot out beams of ionized particles that literally rip holes in the outer cell membranes of infectious microbes and cancer cells. They release spurts of corrosive chemical poisons. They surround, cannibalize, and digest enemy cells—and then recycle the parts. They launch guided missiles from great distances that land and explode with incredible precision. They even smother their enemies in sticky goo (called complement) like the Marshmallow Man in Ghostbusters.
Your immune army deploys these remarkable weapons in multiple wars on several fronts. The skin, respiratory system, intestinal tract and bloodstream sustain the largest exposures and thus contain the most immune cells. Our largest exposure to pathogens—by far—is in the gut. Because this is the largest and most frequently breached barrier, roughly 80% of your white blood cells are embedded just beneath the intestinal mucosal surface. Microbes—in the form of bacteria, fungi, parasites, viruses, and the occasional helminth —are persistently knocking on the door and must be fended off on a non-stop basis. As you will see, we fend with some pretty big sticks. Imagine an army with hundreds of billions of white blood cell soldiers, each fully-equipped to take on cancer cells, viruses, and bacteria mano a mano in a struggle to the death.
Cancer cells are forming continuously in all of us, but alert, activated (you’ll soon see why I italicize this word) immune cells will give them the instantaneous hatchet. If your constantly vigilant and aggressively protective immune system took a coffee break, you’d be dead by the time it was over.
I am going to tell you a lot more about the wondrous, though violent, molecular biological world inside of us. But first, let’s take a look at the “big picture,” an overview of our “War on Cancer.”