In the glycocalyx, act like identification tags that enable the body to distinguish its own cells from foreign and diseased cells.

glycoproteins

Explanation:

Glycoproteins are the proteins to which carbohydrates are attached. The glycocalyx is the covering made up of sugar residues of glycoproteins and glycolipids and is associated with the plasma membrane.  

Glycoproteins of animal cells are exposed to the extracellular surface and are involved in cell recognition. They serve as a tag by which the cells are identified. For example, the glycoproteins of bacterial cells serve as antigens that are recognized by the cells of the immune system of humans. However, these cells recognize the glycoproteins present on the cells of own body as "Self". Likewise, specific glycoproteins present on the surface of RBCs determine the blood type as A, B, AB or O.

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