The first T cell is residual antigen (needed to stimulate antibodies) that remains in the lymph nodes for weeks after the initial infection has been cleared. The second is an "imprinting event" that instructs the T cells to specifically seek a target organ (in the case of flu, the lung). This imprinting event directs the T cells to where the original infectious agent entered the body and, importantly, where the cells need to go to fight future infections.

This new information has major implications for future vaccine research and could lead to the development of vaccines designed to promote immunity to respiratory infections.

Researchers are hopeful that, with further study, it may be possible to protect the population by prepositioning flu-fighting T cells in the lungs so they are in place when the body needs them.

Source: Trudeau Institute