The Song of the Cell: An Exploration of Medicine and the New Human

by Siddhartha Mukherjee

Antigen processing and presentation to CD4 and CD8 cells—the mainstays of T cell recognition—are slow but painstakingly methodical processes. Unlike an antibody, a gunslinging sheriff itching for a showdown with a gang of molecular criminals in the center of town, a T cell is the gumshoe detective going door to door to look for perpetrators hiding inside. In The Lives of a Cell, Lewis Thomas wrote: “Lymphocytes, like wasps, are genetically programmed for exploration, but each of them seems to be permitted a different solitary idea. They roam through the tissues, sensing and monitoring.” Unlike the B cell, though, the T cell isn’t looking for a culprit to come bursting out of the saloon, guns a-blazing. It is, like some omniscient Sherlock Holmes with a pipe and an umbrella, seeking the portent of a person. The debris left behind by an inner presence. A torn-up letter, with the fragment of a name, discarded in the trash can outside. (You might think of that crumpled piece of stationery, mounted within a trash can, as a peptide presented on an MHC molecule.)