Functional differentiation and repertoire diversification of T cells derived from single progenitor cells

Functions of T cells derived from single progenitor cells were investigated. B10. Thy-1.1 recipient mice were either whole body-irradiated and marrow reconstituted or thymus-shielded, irradiated and marrow reconstituted, and limited numbers (3 x 10(3) or 6 x 10(3] of a 1:1 mixture of bone marrow cells from C57BL/6 and B6.Lyt-2.1 mice were transferred intrathymically (i.t.). Donor-type (Thy-1.2+) cells of the thymus of a small portion of recipients which expressed the phenotype of either Ly-2.2 or Ly-2.1 but not both were regarded to be a clone of T cells derived from a single progenitor cell, and such clones were assayed for polyclonal helper (Th) and polyclonal cytolytic (CTL) activities as well as alloantigen-specific proliferative (mixed lymphocyte reaction; MLR) and CTL activities. Clones taken 4 weeks after transfer (4-week-old clones) which were generated in the thymus of whole body-irradiated recipients showed polyclonal CTL but not polyclonal Th activity, whereas 4-week-old clones generated in the thymus of thymus-shielded recipients showed both polyclonal CTL and Th activities. Similarly, 4-week-old clones generated in whole body-irradiated recipients responded with CTL to alloantigens when induced in the presence of T cell growth factors but not with MLR, whereas 4-week-old clones generated in thymus-shielded recipients showed both MLR and CTL to alloantigens. Repertoire diversification of 4-week-old clones, however, was incomplete, since clones generated in whole body-irradiated recipient did not necessarily respond with CTL to all alloantigens examined, and those generated in thymus-shielded recipients did not necessarily respond with MLR to all the antigens. On the other hand, T cell clones were shown to fully mature by 7 weeks after transfer in terms of cell function as well as repertoire diversification.