Thousands of amazing things are going on in just one drop of your blood.
Earth’s crammed with heaven and every common bush afire with God; but only he who sees takes off his shoes; the rest sit round it and pluck blackberries.
Perhaps there’s even more truth in those lines today than when the poet Elizabeth Barrett Browning first penned them. For although creation is still ablaze with the glory of God, we all too often miss it.
Let me say up front that biologists are not immune to this tendency. Though we’re privileged to encounter new and exciting facets of God’s glorious creation, the pressures of everyday tasks can overshadow the call to simply “behold.”
Nonetheless, by God’s grace I’ve found that the more I learn about the complexities of cells—and in particular, cells of the immune system—the more I’m compelled to worship our Creator. Indulge me for a few paragraphs as I describe some of the elaborate beauty that resides within our bodies — and perhaps you’ll discover anew a world afire with the glory of God.
Immune System 101
As its name suggests, the immune system is not a discrete entity or organ but actually a complex array of many organs and cells. It includes organs such as bone marrow, which produces all blood cells, and the thymus, which teaches cells to distinguish between cells that don’t belong in your body and cells that do, then trains them not to attack the latter.
It also includes lymph nodes and the spleen, as well as more dispensable organs such as tonsils and the appendix, all of which serve as battlegrounds for the war waged against invading pathogens--bacteria, viruses, and parasites.
The troops that wage the war in these organs are white blood cells. But they don’t all wear the same uniform. These cells include an array of special forces, each with a unique function and with intricate interdependence on each other. I’ve often thought that if the apostle Paul had known about the interplay among blood cells, he might have used that instead of our hands and feet, ears and eyes as his analogy of the body of Christ (see 1 Cor. 12:12-31).
Peering Through the Microscope
To give you a glimpse of this intricacy and interdependency, let me introduce you to the key players of immunity found within our blood.
Imagine that you prick your finger and smear a drop of blood on a microscope slide. You then stain this thin layer of blood cells with a dye that allows you to see details within each cell. As you adjust the focusing knobs of the microscope, you see a myriad of red blood cells magnified 400 times their actual size—they look like pink discs.
Scrolling through the slide you notice scattered throughout the sea of homogeneous red blood cells several considerably bigger, purple cells in a variety of shapes and patterns. These fascinating cells are white blood cells.
Soon you notice that several of these cells appear speckled. Many of them (neutrophils) contain azure-colored specks. Occasionally you see some with large, vivid red spots or huge purple spots (eosinophils and basophils, respectively). These speckled cells belong to a family of cells called granulocytes—so named because they contain granules.
Despite sharing a family name, they have distinctly different functions. The neutrophil lives for only a few days and in its lifetime courses throughout the bloodstream, ready to race to the site of infection, to attack bacteria that invade your body when you get a cut or splinter.
Although eosinophils and basophils also can fight off pathogens, their more infamous distinction is contributing to the symptoms of asthma and allergies. Indeed, the large purple granules of the basophil are packed full of histamine—a protein that allergy sufferers know all too well. Blame those purple spots for your misery.
As you continue to make your way through the microscope slide, you’ll notice several other cells that are irregularly shaped and much larger than any of the other cells. These are monocytes.They are normally found in the blood, but when they enter tissues they mature into related cells called macrophages. The macrophage’s mission is to scan the body for anything foreign or dangerous (bacteria or damaged, dying red blood cells, for example). When it encounters such a foreign or dangerous substance, it engulfs and “eats” it.
Of course the macrophage doesn’t really have a mouth and teeth; rather, when it senses an invader it projects extensions of its membrane, wraps them around the object or cell, and internalizes it. Once the invader is sequestered within the cell, small spheres containing enzymes that function as molecular garbage disposals encapsulate it.
After the enzymes chew up the invader, other small proteins—so-called molecular chaperones—usher the chewed-up bits into complementary-shaped grooves of larger proteins. These larger proteins together with the nestled fragments of the invader then migrate to the surface of the cell, where they are boldly displayed.
What’s the purpose of this elaborate process? Isn’t it enough to simply digest the pathogen and be done with it? Why would a cell want to put it on display? Is it a mark of honor—a victory flag of sorts? Well, not quite.
The macrophage displays the fragments so that another kind of cell—the T-helper lymphocyte—will spot them and do what it does best: help other cells of the immune system.
Now, it’s not just any T-lymphocyte that can latch onto any fragment of pathogen. Rather, there’s enormous specificity: only a small subset of T-cells—about one in every 5,000-10,000—will be able to engage or recognize a given pathogen. Surely such a specialized cell is of great distinction and must have a prominent, notable appearance, right?
Actually, the lymphocyte doesn’t look nearly as flashy as the red-spotted eosinophils. Nor is it as big as the monocyte. In fact, it’s round and plain and not much bigger than a red blood cell.
Its only unique feature is that its nucleus is large and overwhelms nearly the entire cell. But compared to that of the other white blood cells, the nucleus too appears boring—round and plain, lacking segments or distinction.
Yet if Paul were using blood cells in his analogy, this would be one he would refer to as “seemingly weaker and yet indispensable” (1 Cor. 12:22)—for the T-helper lymphocyte is arguably one of the most important cells of the immune system.
When it spies fragments of a pathogen boldly displayed on the surface of a macrophage, it attaches itself and immediately sets into motion a cascade of chemical reactions.
The end result is a fully activated T-cell that produces just the right chemicals to activate two more lymphocytes, which make antibodies and killer T-lymphocytes that kill virally infected cells.
What beauty! What intricacy! And to think all these reactions and interactions are happening between and within cells that are barely visible to the unaided eye.
How small are they? Consider this: the thickness of the page you are holding is about 100 micrometers. The diameter of an average white blood cell is one-tenth of this paper’s thickness.
Put another way, approximately 100 cells could be lined up next to each other and fit across this lowercase o.
When you consider that adults have somewhere between 4,000 to 11,000 white blood cells in every microliter of our blood—and we have on average 5 million microliters of blood coursing throughout our bodies—that’s 20 billion to 55 billion white blood cells. And if each cell was the letter o and these letters were typed end to end without any breaks, they would fill 16 million pages—or about 340,000 copies—of The Banner!
Without our awareness or instruction every single one of those cells is pulsating with thousands of intricate chemical reactions every minute!
What splendor! What complexity! Upon seeing it I’m compelled to exclaim with the psalmist:
O Lord, our Lord, how majestic is your name in all the earth!
You created my inmost being; you knit me together in my mother’s womb.
I praise you because I am fearfully and wonderfully made (Ps. 8:1;139:13-14).
When Good Cells Go Bad
Although awed by the wonders within, some of you reading this are all too familiar with the sad irony that the very cells in which we see such complexity and glory exist for the purpose of fighting off pathogens—agents that often deliver pain and suffering. And at times those very same cells turn against our own bodies, afflicting us with autoimmune diseases such as multiple sclerosis, lupus, rheumatoid arthritis, or fibromyalgia.
Despite its intricacy and splendor, all of creation—including our cells—groans to be fully released from the effects of the fall.
Yet while we wait and eagerly long for God to make all things new, we also take comfort that God has not forgotten us and has not left us in a world that’s spinning out of control (Col. 1:16-17). Rather, we have assurance that the very same God who flung the stars into place by the breath of his mouth is the same God who knit us together in our mother’s womb. God knows us intimately and perceives our thoughts from afar (Ps. 139:2). He has not left us alone to suffer hopelessly but has sent us a Counselor and Comforter (John 14:26).
Gradually, as the Holy Spirit opens our eyes we realize that, despite the thorns, we are in the midst of a glorious blackberry patch . . . and we kick off our shoes, for we recognize we are standing on holy ground.