Also known as transferrin, this glycoprotein is a non-heme iron binding protein. Lactoferrin is commonly found in milk. It contributes to milk's antimicrobial activity by sequestering free iron, making it unavailable for microbial replication. It can also be bound in the granules of leukocytes available for immediate release.

Lactoferrin is also known to interact with CD14 and inhibit expression of cell adhesion molecules, making it immunomodulatory. Though it is not classified as a cytokine, it posesses cytokine like activities in modulating various cellular functions, including:

Hematopoiesis.
Immunomodulation - including reduction of inflammation and shock.
Cellular Proliferation.
Growth Factor - including Bone Marrow
Cell Survival Factor - promoting cell survival in serum starved cells.

Lactoferrin is a common ingredient in chemically defined and serum free medias because of these cytokine like properties. However, it has also been shown to be immunomodulatory. It suppresses antibody production in B-cells, modulates natural killer cell activity. It can also modulate inflammation by competing with chemokines for receptors, interferring with epidermal cytokine production, downregulating cellular adhesion molecules, and by stimulating the relase of IL8, an immunomodulatory cytokine. When given to monocytes and macrophages, it will reduce interleukin 1 (IL1) production, along with the various IL1 regulated cytokines and colony stimulating factors.

Lactoferrin also appears to be involved in angiogenesis, significantly enhancing VEGF but not FGF-basic (bFGF) mediated angiogenesis, though it has a negative effect on tumor induced angiogenesis

The functions of lactoferrin are diverse and poorly understood. However, it is evident that Lactoferrin is an important modulator of inflammation, a growth factor, a regulator of uncontrolled cytokine production (cytokine storm), and innate antibiotic, acting through both direct and indirect mechanisms.