Ferritin is a protein found in humans (and most other life on earth) involved in iron storage (1). This 24 subunit protein is made of heavy (H) and light (L) subunits. The ratio of subunits in the protein depends on the type of tissue it is in and the stage of development of the organism (2). Mitochondrial ferritin has also been detected as a pro-protein.
Ferritin light chain (or light polypeptide) mainly acts as an iron reservoir and to remove excess iron from the body. Ferritin heavy chain (or heavy polypeptide) is a ferroxidase enzyme that catalyzes the oxidation of iron II to iron III for proper storage in a soluble and non-toxic state (2). Mitochondrial ferritin (MtF) also acts as a ferroxidase enzyme to oxidize iron II to iron III for storage. Mitochondrial ferritin is inactive in the pro-protein state but is processed into a mature and functional protein after uptake by a mitochondrion (3).
As ferritin is involved in iron storage, it plays an indirect part in oxygen distribution through hemoglobin and myoglobin. Recently, ferritin’s role in several other physiological processes has also been discovered, including angiogenesis, inflammation, immunity, signalling and cancer (4-8).
Ferritin can also be used as a clinical tool to test for some common iron-related diseases, such as iron-deficiency anemia (9). Ferritin levels are indirectly used to measure the amount of iron in the body as the amount of ferritin in blood serum correlates to the amount of total iron stored.
More recently, ferritin has also been used as an important biomarker to predict the outcome of coronavirus disease 2019 (COVID-19) patients (10, 11). Elevated ferritin levels were associated with more severe disease and worsening prognosis for patients. Patients with severe COVID-19 often have an extreme and uncontrolled immune response (also known as a cytokine storm), in which excessive amounts of inflammatory cytokines (TNFα, IL-6, IL-12, and IL-8) are released over the course of the disease. As the levels of cytokines increase, the levels of serum ferritin also increase.
Reddot Biotech carries ELISA kits for all three types of ferritin found in humans:
Our COVID-19 related ELISA kits can be found here.
References and further reading: