Milk-derived osteopontin influences the composition of the intestinal intraepithelial lymphocyte compartment

Osteopontin is a protein with many physiological roles widely expressed by many cell types, tissues, and bodily fluids, including breastmilk. The functions of breastmilk osteopontin are not clearly defined, however, it is known to impact intestinal and brain development in infants. Although it has been shown that endogenous osteopontin influences the survival of intestinal intraepithelial lymphocytes (IEL), the impact of milk osteopontin on developing intestinal immune cells remains unclear. In this report, mouse models lacking expression of osteopontin were used to demonstrate that milk-derived osteopontin is important for the development of IELs, with observed effects in both juvenile and adult mice. These changes are most prevalent in IELs expressing CD8αα: however, the impact of these alterations is unclear, as mice with disrupted IEL compartments are not more susceptible to intestinal inflammation induced by DSS or Citrobacter rodentium infection.