Immune: A Journey Into the Mysterious System That Keeps You Alive

by Philipp Dettmer

Let us summarize one last time because this stuff is really important and really hard: To activate your Adaptive Immune System, a Dendritic Cell needs to kill enemies and rip them into pieces called antigens, which you can imagine as wieners. These antigens are put into special molecules, called MHC class II molecules, that you can imagine like hot dog buns. On the other end, Helper T Cells rearrange gene segments to create a single specific receptor that is able to connect to one specific antigen (a specific wiener). The Dendritic Cell is looking for just the right Helper T Cell that can bind its specific receptor to the antigen. And if a matching T Cell is found the two cells interlock. But then there needs to be a second signal, like a gentle encouraging kiss on the cheek, that tells the T Cell that all is good and the signal from the presented antigen is real. And only then does a Helper T Cell activate.