Sodium is a metal where humans have discovered a great deal of its total roles in the body as well as being one of the only two alkali metals that play a major role in the bodily functions. It plays an important role in maintenance of the cell membrane potential and the electrochemical gradient in the body via the sodium-potassium pump and sodium-glucose transport proteins. Sodium also serves a purpose in the nervous system and cell communication as they flood into axons during an action potential to preserve the strength of the signal. It has also been shown that sodium affects immune response both in efficiency and speed. Macrophages have increased proliferation rates at high-salt concentrations and the body uses high-sodium concentrations in isolated regions to generate an heightened immune response which fades after the infection has been dealt with.