Working together, IL-15 and IL-2 help to provide equilibrium to the immune system. When an immune response to an antigen is mounted, IL-15 is produced, which causes T cells to divide and attack the invader and stimulates "memory" T cells. At the same time that IL-15 production increases, IL-2 controls the proliferation of "memory" T cellscaused by increasing amounts of IL-15by killing some T cells as they divide.
"In immune responses," Dr. Marrack said, "the stimulatory effects of one cytokine are frequently counterbalanced by the inhibiting effects of another cytokine. This balance allows the immune system to battle antigens with a controlled response."
Interleukins are a cytokines, proteins, that are secreted by different types of cells in the body, and which regulate the intensity and length of immune responses.
National Jewish scientists believe that this information could help doctors create better treatments in the future for immune diseases such as AIDS, lupus or rheumatoid arthritis. In the future, doctors may be able to use this knowledge to regulate the division of T cells. Changing the balance of the proteins that affect T cellsin effect regulating the immune response to an antigencould be used successfully with medical therapies.
"You might be able to attack that balance by changing either IL-2 or IL-15," Dr. Marrack said.