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

by Philipp Dettmer

Step 1: A battle needs to occur and dead enemies, which are big chunks of antigens (turkey drumsticks), need to float through the lymph node. Here, a B Cell, with a specific receptor needs to connect to the antigen. If the dead enemy is covered in complement, activation will be much easier. This will activate the B Cell, which makes a lot of copies of itself and produces low-grade antibodies, but the B Cells will die after around a day if nothing more happens. Step 2: In the meantime, a Dendritic Cell needs to pick up enemies at the battlefield and turn them into antigens (wieners) which are put in the MHC class II molecules (hot dog buns) and travel to the T Cell dating area in the lymph node. Here it needs to find a Helper T Cell that is able to recognize the antigen with its unique T Cell receptor (eat the wiener from the bun). If this happens the Helper T Cell is activated and makes a lot of copies of itself. Step 3: The B Cell breaks the big chunk of antigen (turkey drumstick) down into dozens or hundreds of small antigens (wiener sized) and begins presenting them in MHC class II molecules (hot dog buns). Step 4: An activated B Cell that is presenting hundreds of different antigens (wiener-sized sausage pieces) needs to meet a T Cell that can recognize one of these antigens with its specific T Cell receptor, which is the second signal for the B Cell. Only if this exact sequence of events occurs does a B Cell get activated for real. Are you impressed yet with your biol...