CD8αα-mediated intraepithelial lymphocyte snatching of thymic leukemia MHC class Ib molecules in vitro and in vivo

Thymic leukemia (TL) is a MHC class Ib molecule that interacts with CD8 alpha alpha homodimers. CD8 alpha alpha is abundantly expressed by intraepithelial T lymphocytes (IELs) located in close proximity to TL-expressing intestinal epithelial cells. In this study, we show that CD8 alpha alpha(+) IELs snatch TL from the plasma membrane of TL-expressing cells and express TL in its proper orientation on their own cell surface. TL snatching is enhanced by cross-linking of IEL TCRs in a phosphatidylinositol kinase-dependent manner, and results in overall alterations to the IEL cell surface detected by enhanced binding of peanut agglutinin lectin. Induction of bowel inflammation results in the presence of TL on IELs, probably via in vivo snatching, providing the initial evidence for the interaction of CD8 alpha alpha IELs with intestinal cells.