||Transferrin is a monomeric glycoprotein found in plasma at an average concentration of 250 mg/100ml. The specific iron-binding protein in plasma, it has a role in the transportation and distribution of iron among the body organs, in iron metabolism and in prevention of iron loss via the kidney. Stored in bone marrow as TF-bound iron, it also possesses bacteriostatic and fungistatic activity. Clinically, decreases in transferrin are observed in congenital disorders, newborns, inflammatory diseases, hypo-proteinemias and nephritic syndrome; increases are found in pregnancy, iron-deficiency anemias and inoculation hepatitis. Transferrin is required by all types of cells in cultures for maximal growth. It is, therefore, an important factor used in defined culture media.