Intestinal T Cells in CD8α Knockout Mice and T Cell Receptor Transgenic Mice

Abstract

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.