Is it true that substances are carried from the blood in capillaries to tissues in a liquid called tissue fluid? What is the extracellular fluid in most tissues is called? What is a tissue fluid?   Tissue fluid is the the fluid that surrounds the bodies cells, or technically it bathes the cells in the body or cleans them.
The most important function of immune system is to defend the body from different disease causing pathogens. Whenever there is pathology in human body, immune system is activated to protect the vital tissues from harm.
One of the most important functions of the macrophages is that they can activate the acquired immune system! After a macrophage has eaten and digested a particle, it displays some of the broken down germ proteins (antigens) on its cell surface.