White blood cells are a key part of the immune system. They fight foreign invaders, like viruses and bacteria, but also are involved with inflammation. Substances produced by white blood cells include lactoferrin and myleoperoxidase. Lactoferrin has antimicrobial activity. Myloperioxidase is also part of the body’s defense system; it acts as an oxidizing agent and is involved with inflammation.
A study published in the Journal of Complementary and Integrative Medicine (2015 Dec;12(4):277-82. doi: 10.1515/jcim-2014-0042) looked at whether green tea extract could enhance white blood cell function. Volunteers were asked to take 300 mg of the green tea extract daily for 14 days and the capacity of circulating white blood cells to release both myeloperoxidase and lactoferrin was assessed. The researchers concluded that a green tea extract when taken as a dietary supplement for 14 days can increase the leukocyte activity and the total plasma antioxidant status and may have role to play in the prevention of inflammatory disease.