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

by Siddhartha Mukherjee

It is one of the cleverest ways of repurposing a cell’s intrinsic molecular apparatus: it takes the natural waste-disposal factory of the body, treats the viral protein as if it were any other protein meant for disposal, mounts it on a protein carrier, and pushes it out of a hatch and onto the cell’s surface. The inside is now outside. The cell has sent a sampling of its inner life, bound in the correct frame, to be surveyed by the immune system. When a CD8 cell comes by, sniffing the cell surface, it will find a large selection of peptides from the interior of a cell loaded on its surface—including, of course, the peptide from the virus. And only if that foreign peptide is presented by the self MHC (the altered self) will it trigger an immune response, killing the infected cell.