Scientists at the Garvan Institute of Medical Research in Sydney, Australia, have identified a previously unknown micro-organ within the immune system, which could lead to new approaches for developing more effective vaccines. Discovered in mice using a live imaging technique known as two-photon microscopy, the thin, flattened structures, given the name subcapsular proliferative foci (SPF),  are located over the surface of draining lymph nodes, and act as a congregation point for immune cells preparing to respond to previously encountered infections. 

Using the 3D microscopy technique, the researchers saw how memory B cells (MBCs) and other immune system cells homed in on the SPF structure, and how the passive MBCs were transformed into activated plasma cells, a population of immune system cell that secretes infection-fighting antibodies against known invaders. It was exciting to see the memory B cells being activated and clustering in this new structure that had never …