What fluid leaves the blood capillaries but does not return to the blood?

Red blood cells does not have a direct contact with the body cells.A substance called the tissue fluid does.It leaks out from the blood capillaries carrying oxygen and food substance to the body cells.It then carry waste materials out of the body cells.However, some of this substance does return to the blood while some are collected in the lymph vessel.The tissue fluid in the lymph vessel is called lymph.