Dendritic cells, shown here in an electron microscopic picture, need antibodies produced by B cells for their maturation. Dendritic cells, or DCs for short, perform a vital role for the immune system: They engulf pathogens, break them down into their component parts, and then display the pieces on their surface. This in turn signals other immune cells capable of recognizing these pieces to help kick-start their own default program for fighting off the invaders. In order to do their job, the DCs are dependent upon the support from a class of immune system molecules, which have never before been associated...