Molecular characterization of gut T cell precursors in euthymic and athymic mice
The major compartment of effector T cells in the body lines the epithelium of the murine gut. Intraepithelial T lymphocytes (T-IEL) from this location have large intracytoplasmic storage granules containing perforin and granzyme and express y-INF mRNA.Ex vivothey secrete this lymphokine and kill target cells immediately1 3. The number of these T cells is comparable to that of all T cells present in both spleen and lymph-nodes4. T-IEL have different origins in normal mice5-9. About half derive from activated T cells migrating from the peripheral lymphoid organs to the gut and have a memory phenotype (TcR-aß+CD5+CD28+LFA-1+CD44+CD8aß+or CD4+thymus-dependent-IEL/TD-IEL). The other half differs from peripheral T cells by phenotype (CD8aa+CD5-LFA-Y B220+) and CD3 complex expression (CD3-4 chain is associated with a analogue, the FcERIy chain10). They comprise a large proportion of TcR-y8+cells, and the TcR-aß+cells of this lineage are not deleted by self antigens4°11’12. CD8aa T-IELs are thought to develop locally: structures named cryptopatches, disseminated randomly at the base of some gut crypts containing TcR-Thy1+c-kit+IL-7R+CD25+cells13,14were assimilated to “local” thymus like structures harboring differentiating precursors14,15Although CD8aa T-IELs are generated in athymic mice, the presence of a thymus increases their number by five-to 10 fold and modifies their composition5’7’16. In euthymic mice, TcR-aß and TcR-y6 T cells are equally represented. In athymic mice about 90-95% of TcR+T cells are y8+. These differences remain after the injection of peripheral T cells(what reconstitutes TD-IEL), and thus are not due to any role of the TD-IEL on the maturation or expansion of CD8aa T-IEL.
KeywordsAthymic Mouse Intraepithelial Lymphocyte Chain Rearrangement Ectopic Thymus Euthymic Mouse
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