Presence of intestinal intraepithelial lymphocytes in mice with severe combined immunodeficiency disease

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Abstract
The murine intestinal epithelium contains a heterogeneous population of intraepithelial leukocytes (IEL) most of which are granulated, Thy‐1‐CD5−CD8+. In order to assess the lineage relationship of this subgroup of IEL to peripheral T cells, we examined IEL in mice with the severe combined immunodeficiency (scid/scid) mutation, which lack T and B cells in peripheral lymphoid tissues. Electron and light microscopy showed that the intestine from scid/scid mice had granulated IEL similar to IEL in normal C.B‐17 mice. Flow cytometry of isolated IEL stained with monoclonal antibodies against Thy‐1, CD3, CD4, CD5 and CD8 showed that scid/scid mice IEL contained cells with the Thy‐1−CD4−CD5−CD8+ phenotype. Immunohistochemical staining of IEL in tissue sections with antibodies to Thy‐1 and CD8 confirmed that the Thy‐1−CD8+ cells were in the intestinal epithelium. These scid/scid IEL also lacked CD3 expression and mRNA for the Vγ7 V region gene of the γ T cell receptor. We conclude that scid/scid mice contain precursors for IEL that can differentiate into a granulated Thy‐1−CD5−CD8+ IEL in the intestine. The absence of CD8+ peripheral T cells in these mice suggests that these IEL differ from classical T cells in their ability to differentiate and express CD8 and do not require T cell receptor expression for their localization to the intestine.