The fractionation and characterization of bovine tear proteins, especially lactoferrin

Gentle procedures are described for the fractionation of bovine tear fluid by a combination of centrifugation, salt precipitation, gel filtration and ion exchange chromatography. Fractions are examined by gel electrophoretic immunological methods. Reference patterns are compiled and compared with bovine milk and serum patterns. Properties of some of th components are determined. Lactoferrin is isolated in two separate, but closely related, fractions. An acidic protein with a molecular weight of 23 000 daltons, is also isolated. Distinct heterogeneity is observed between individual animals, suggestive of a genetic polymorphism. A method is presented for the determination of the antibacterial activity of tear fluid and its fractions.