Intestinal T Cells in CD8α Knockout Mice and T Cell Receptor Transgenic Mice
T cells distributed at the epithelium of the intestines are called intraepithelial lymphocytes (IEL). IEL are heterogenous populations comprising of αβ and γδ T cells. The majority of IEL express CD8 mainly as homodimers of the a subunit (CD8αα), whereas T cells in other peripheral lymphoid organs express CD8 as heterodimers of the α and β subunits (CD8αβ) (reviewed in Ref. 3). Autoreactive T cells have been reported to be present in IEL population4 and therefore IEL are suggested to mature through an extra- thymic pathway. In the CD8α knockout mice, the CD8 co-receptor was shown to be required for thymic ontogeny of cytotoxic T cells but not helper T cells.1 In the H-Y transgenic mice, CD8+ T cells with the male H-Y antigen specific T cell receptor are thymically deleted in the male but selected in the female mice.2 In this report, the criteria for the ontogeny and function of IEL were studied in the CD8α knockout mice and in the H-Y T cell receptor transgenic mice. In these transgenic and knockout models, the antigen specificity of IEL can be defined by the H-Y specific T cell receptor and the defects observed for IEL in CD8α knockout mice would be a reflection of the indispensable role of CD8α in the ontogeny and function of IEL.
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