Failure of t cell receptor negative selection in murine intestinal intra-epitheliallymphocytes

The intestinal intra-epithelial lymphocytes (IEL) are divided into several subsets on the basis of expression of T cell receptor (TCR) a/3 and y6, intensity of Thy-1 expression and expression ofLyt-3 chain. To investigate the differentiation pathway of the IEL, we examined the repertoire of\f₀ segments of T cells in the IEL in BALB/c (H-2^d, Mls-1^b2^a) or AKR/J (H-2^k, Mls-1^a2^b) mice. Among freshly isolated IEL, an appreciable number of T cells bearing V_β3 or V_β11, which recognize Mls-2^a- or MHC IE-encoded molecules respectively, were detected in BALB/c mice.Similarly, in AKR/J mice, IEL contained appreciable levels of V^6-bearing T cells. V_β3- orV_β11 -bearing T cells in the IEL in BALB/c mice increased to a significant level when incubatedwith staphylococcal enterotoxin A which specifically stimulates V₀3- and Vg11 -bearing T cells.Most of IEL without clonal deletion expressed Lyt-2 but not Lyt-3 antigens. Such T ceils werehardly detected in other organs, including liver. Our results indicate that TCRa/3-bearing intestinalIEL that have not undergone negative selection may have differentiated outside the thymus, presumably at a local site of the intestine and can respond normally to the signal via their TCR.