What are two functions of cell surface markers?

There are 2 functions for cell surface markers. The first is to recognize the outside cell. The second is to allow the cell to bind to substances outside the cell. Cell surface markers are proteins expressed on the surface of cells that often conveniently serve as markers of specific cell types. There are different types of cell surface markers. These markers are vital for the human body to function. These markers also vitally affect the functions of other biological systems of other organisms and creatures such as animals.