Human Errors: A Panorama of Our Glitches, from Pointless Bones to Broken Genes

by Nathan H. Lents

A fledgling embryo develops immune cells while in utero. The very first thing that these cells do is participate in a phenomenon called clonal deletion. Clonal deletion is the process by which the developing immune cells in a fetus are presented with small bits of chewed-up proteins from the fetus’s own body. The immune cells that react to those bits of self-protein are then eliminated; they are “deleted” from the immune system. This process goes on for weeks and weeks, and the goal is to eliminate every single immune cell that has the potential to react to its own body. Only then is the immune system ready for action.

A fledgling embryo develops immune cells while in utero. The very first thing that these cells do is participate in a phenomenon called clonal deletion. Clonal deletion is the process by which the developing immune cells in a fetus are presented with small bits of chewed-up proteins from the fetus’s own body. The immune cells that react to those bits of self-protein are then eliminated; they are “deleted” from the immune system. This process goes on for weeks and weeks, and the goal is to eliminate every single immune cell that has the potential to react to its own body. Only then is the immune system ready for action.