The Invisible Kingdom: Reimagining Chronic Illness

by Meghan O'Rourke

Immunology uses the term “regulation” to describe the body’s mechanisms for calling its army of immune cells back and turning off their destructive power. As Caleb put it one day, in a metaphor I would find repeated elsewhere, “The T cells are like cadets, sent out to attack viruses. But they have little self-control, and so they are monitored by sergeants, known as ‘regulatory T (Treg) cells,’ who tell them the attack is over and it’s time to head back to the base. When the regulatory T cells aren’t working, you get an out-of-control immune response, making you sicker than you need to be.” One reason people feel sick when they have an infection is that the inflammatory response of the immune system itself makes them feel sick—something I had failed to understand previously. (This is also why many people feel briefly sick after getting, for example, a COVID-19 vaccine—a vaccine, after all, is designed to provoke an immune response.) The cell that has found a virus or bacterium uses chemicals called “chemokines” and “cytokines” to recruit an inflammatory response, calling for white blood cells. These chemicals work on a gradient—like a radar signal that gets stronger and louder as you approach the targeted object. Or, as Caleb memorably described this process to me, “They’re drawn to the center of the infection or wound, as if by Gandalf striking his staff and saying, ‘I call you to come fight evil,’ ” he explained, using an analogy any Lord of the Rings fan could follow. T...