Fidelity of the repertoire in T cell reconstituted athymic nude rats. Preservation of a deficit in alloresponsiveness over one year

A single intravenous injection of a relatively small number of T cells contained in the population of rat thoracic duct lymphocytes (TDL) is sufficient to restore to normal the peripheral T cell pool of athymic PVG.rnu/rnu nude rats. The donor T cells expand greater than 10-15-fold, self-renew, and restore immunocompetency to nude recipients permanently (greater than 2 yr). We asked whether the T cell repertoire was affected by the expansion and self-renewal process. Nude recipients were injected with syngeneic PVG TDL that had been allospecifically depleted (negatively selected) by consecutive passage from blood to thoracic duct lymph through two irradiated (DAxPVG)F1 intermediate rats. Negatively selected TDL were tested before transfer by the P----F1 popliteal LN GVH assay and showed a greater than 90% depletion of specific reactivity to DA alloantigens. Surviving cells or their progeny were recovered from LN or TDL of nude recipients 8 and 12 mo after transfer. The deficit in GVH reactivity to the DA haplotype persisted, but normal GVH activity was demonstrated against a third party (AOxPVG)F1 alloantigen. The "hole" in the repertoire could not be attributed to tolerance induced by the co-transfer of contaminating irradiated F1 TDL. PVG TDL passaged consecutively through (AOxPVG)F1 and (DAxPVG)F1 intermediates and devoid of (AOxPVG)F1 cells remained specifically depleted to both AO and DA haplotypes when recovered from nude recipients 4 and 13 mo later, but displayed GVH activity to a third-party (BNxPVG)F1 alloantigen. Thus the exact specificity of the T cell repertoire of the original inoculum was faithfully maintained in nude recipients throughout the initial phase of rapid expansion and the continued self-renewal of the mature peripheral T cell pool.