Strain-specific TCR repertoire selection of IL-4-producing Thy-1(dull) gamma delta thymocytes

Thy-1(dull) gamma delta thymocytes constitute an unusual subset of mature T CR gamma delta cells which share with NK T cells the expression of cell sur face markers usually associated with activated or memory cells and the simu ltaneous production of high levels of IL-4 and IFN-gamma upon activation. I n DBA/2 mice, Thy-1(dull) gamma delta thymocytes express a restricted reper toire of TCR that are composed of the V gamma1 gene product mainly associat ed with V delta6.4 chains exhibiting very limited junctional sequence diver sity. In this study we have characterized this gamma delta T cell populatio n in different strains of mice and show that Thy-1(dull) gamma delta thymoc ytes are present in every strain tested, albeit at different frequencies. M oreover IL-4 production by gamma delta thymocytes is mainly confined to the Thy-1(dull) gamma delta population in every strain tested. Finally, the re pertoire of TCR expressed by Thy-1(dull) gamma delta thymocytes varies in d ifferent strain of mice, although a biased expression of V gamma1 and V del ta6 chains was observed in all strains studied. However, the extent of junc tional diversity of the V gamma1 and V delta6 chains expressed by Thy-1(dul l) gamma delta thymocytes varied from oligoclonal in DBA/2 mice to polyclon al in FVB/N mice. Thy-1(dull) gamma delta thymocytes from mouse strains suc h as C3H/HeJ and BALB/c contain cells with diverse V delta6(D)J delta junct ions together with cells with relatively homogeneous V delta6(D)J delta jun ctions, similar to those found in DBA/2. Thus, the Thy-1(dull) gamma delta population appears to contain two subsets of cells which differ in the dive rsity of their TCR.