Blood types are determined by the presence of protein located on

Red blood cells.

Explanation:

Our blood is made up of blood cells and plasma which is an aqueous fluid. Blood type is determined by the identifiers presence and absence which is present on the surface of red blood cells. These identifiers are known as antigens which helps in the immune system to identify its own red blood cell types.

There are 4 types of blood type:

A, B, O, and AB. These blood types are determined with the help of the antigen which is present on the surface of the blood cell and antibodies which is present in the plasma.