Preferential accumulation of CD103+ T cells in human livers; its association with extrathymic T cells

Background/Aims: CD103, a mucosal integrin αEβ7, binds to E-cadherin expressed on hepatocytes and bile duct epithelium in the liver. Although CD103+ T cells are enriched in intestinal intraepithelial lymphocytes, the localization of those cells in the liver is unknown Methods: We investigated whether CD103+ cells are present in human livers, and how they are associated with the intrahepatic development of T cells by flow cytometry and immunohistochemistry. Results: Human livers contain significantly (P<0.001) higher percentages of CD103+ cells in CD4+ and CD8+ T cells (25.7±13.5 and 27.1±19.3%, respectively) than peripheral blood lymphocytes. Moreover, CD103+ cells in the liver, but not in peripheral blood, contained T cells with intermediate expression level of T cell receptor αβ. Those cells consist of mostly CD4+ and CD4−CD8− cells, and expressed low level of CD56 and interleukin-2 receptor beta chain in most of the population. These characteristics are distinct from natural killer T cells, which have been thought to be extrathymic T cells in human livers. Moreover, intrahepatic CD103+ cells expressed mRNA for recombination-activating gene-1, -2 and pre T cell receptor-alpha detected by reverse transcription-polymerase chain reaction Conclusions: CD103+ T cells are preferentially accumulated in human livers, and those T cells show characteristics of extrathymic T cells.