The appearance of Thy-1- donor T cells in the peripheral circulation 3-6 weeks after bone marrow transplantation suggests an extrathymic origin

Donor and host T cells were distinguished by T cell antigen marker Thy-1 isotype and cytoplasmic isozyme Gpi-1 in this study of bone marrow transplantation between congenic mice. During the first 3-6 weeks after irradiation and marrow transfer, percentages of cells bearing the donor Thy-1 isotype in the periphery are much lower than percentages of T cells bearing the donor Gpi-1 marker. Apparently a population of Thy-1- donor T cells exists for several weeks after bone marrow transplantation. Further study showed that this population of CD3+, Thy-1- donor T cells expressed CD4+ or CD8+ and was found in peripheral blood and spleen but not in the thymus. This finding suggests their extrathymic origin.

Intratumor gene expression after adoptive immunotherapy in a murine tumor model. Regulation of messenger RNA levels associated with the differential expansion of tumor-infiltrating lymphocytes

The aim of this paper was to show that the adoptive immunotherapy (AIT) of established tumors resulted in the activation of defined lymphocyte-associated genes at the site of rejection. C57BL/6J mice bearing the moderately immunogenic syngeneic MCA/76-9 sarcoma received combination therapy 10 days after tumor cell implantation. This consisted of a single i.p. injection of cyclophosphamide (CY) followed by the i.v. injection of tumor-sensitized T cells (CY/AIT). The previously observed in situ differential expansion of tumor-infiltrating lymphocytes (TIL) was associated with a parallel modulation of CD4 (L3T4) and CD8 Ag expression. Flow cytometric analysis indicated that the CD8+ TIL appeared to contain two subpopulations during the reported proliferative phase, but by day 8 after CY/AIT the cells were composed of a single bright population. The CD4+ TIL similarly appeared to show two subpopulations, but in contrast to the CD8+ TIL there was a shift to a predominantly less bright single population by day 8. The expression of lymphocyte genes (Ly-2 and Ly-4 encoding the CD8 and CD4 Ag, respectively, IL-2, IL-2R, IFN-gamma, and IL-6) was analyzed by Northern hybridization using RNA extracted from whole tumor tissue. Progressing tumors expressed only low and relatively constant levels of mRNA for all of the genes except Ly-2 over a 19-day period. In contrast, there were considerable temporal fluctuations in mRNA levels depending on whether the mice had received CY or CY/AIT, but it was apparent that CY/AIT induced the more dramatic changes as far as Ly-2, Ly-4, IL-2, and IFN-gamma mRNA levels were concerned. A preliminary survey of cytokine bioactivity released by tumor-associated cells isolated 9 days after CY/AIT indicated that both IFN-gamma and IL-6 activities were released by the cells, but not IL-2, despite the relatively high levels of IL-2 mRNA. These data provide evidence that the differential expansion of TIL after CY/AIT is accompanied by well defined changes in the levels of mRNA-encoding TIL membrane Ag and lymphokine genes and are concordant with the view that amplified anti-tumor immune responses occur after AIT.

Intratumor gene expression after adoptive immunotherapy in a murine tumor model. Regulation of messenger RNA levels associated with the differential expansion of tumor-infiltrating lymphocytes

The aim of this paper was to show that the adoptive immunotherapy (AIT) of established tumors resulted in the activation of defined lymphocyte-associated genes at the site of rejection. C57BL/6J mice bearing the moderately immunogenic syngeneic MCA/76-9 sarcoma received combination therapy 10 days after tumor cell implantation. This consisted of a single i.p. injection of cyclophosphamide (CY) followed by the i.v. injection of tumor-sensitized T cells (CY/AIT). The previously observed in situ differential expansion of tumor-infiltrating lymphocytes (TIL) was associated with a parallel modulation of CD4 (L3T4) and CD8 Ag expression. Flow cytometric analysis indicated that the CD8+ TIL appeared to contain two subpopulations during the reported proliferative phase, but by day 8 after CY/AIT the cells were composed of a single bright population. The CD4+ TIL similarly appeared to show two subpopulations, but in contrast to the CD8+ TIL there was a shift to a predominantly less bright single population by day 8. The expression of lymphocyte genes (Ly-2 and Ly-4 encoding the CD8 and CD4 Ag, respectively, IL-2, IL-2R, IFN-gamma, and IL-6) was analyzed by Northern hybridization using RNA extracted from whole tumor tissue. Progressing tumors expressed only low and relatively constant levels of mRNA for all of the genes except Ly-2 over a 19-day period. In contrast, there were considerable temporal fluctuations in mRNA levels depending on whether the mice had received CY or CY/AIT, but it was apparent that CY/AIT induced the more dramatic changes as far as Ly-2, Ly-4, IL-2, and IFN-gamma mRNA levels were concerned. A preliminary survey of cytokine bioactivity released by tumor-associated cells isolated 9 days after CY/AIT indicated that both IFN-gamma and IL-6 activities were released by the cells, but not IL-2, despite the relatively high levels of IL-2 mRNA. These data provide evidence that the differential expansion of TIL after CY/AIT is accompanied by well defined changes in the levels of mRNA-encoding TIL membrane Ag and lymphokine genes and are concordant with the view that amplified anti-tumor immune responses occur after AIT.

Increased number of Leu-2-bearing non-T cells with natural killer activity in chimpanzees

Peripheral blood lymphocytes from adult and adolescent chimpanzees, as well as adult humans, were studied for phenotypic surface markers by flow cytometry. Lymphocytes from chimpanzees were found to have increased numbers of Leu-1-, Leu-2+ cells as compared to humans. These cells, following preparative electronic cell sorting, were shown to possess natural killer function. Further analysis of this subpopulation indicated that they lacked responsiveness to a number of T-cell mitogens. The differences in lymphocyte subpopulations between chimpanzees and humans can almost be totally accounted for by the Leu-1-, Leu-2+ cells. Phylogenetic disparity between these two species may also be found within this population.

Early T lymphocytes. Differentiation in vivo of adult intrathymic precursor cells

A minor subpopulation of adult murine thymocytes (less than 5%) that is Lyt-2-, L3T4-, and expresses low levels of Ly-1 (designated dLy-1 [dull] thymocytes) has been identified, isolated, and characterized. This study assesses the differentiation potential of dLy-1 thymocytes in the thymus in vivo. Using multiparameter flow cytometry, radiation chimeras of C57BL/6 mice congenic at the Ly-1 or Ly-5 locus, and allelic markers to discriminate host and donor, we showed that transferred dLy-1 cells were able to generate thymocytes expressing both cortical and medullary phenotypes in a sequential manner. The proportion of donor-derived thymocytes obtained was directly related to the number of dLy-1 thymocytes transferred. Transfer of purified Lyt-2+ or Lyt-2+ + L3T4+ thymocytes, which constitute greater than 94% of total thymocytes, failed to generate any donor-derived thymocytes in irradiated recipients. Transfer of bone marrow (BM) cells produced the same sequential pattern of differentiation as that produced by dLy-1 cells, but was delayed by 4-5 d. Transferred dLy-1 thymocytes exhibited a limited capacity for self-renewal, and resulted in a single wave of differentiation in irradiated hosts. Thus, thymic repopulation by donor-derived cells after transfer of dLy-1 thymocytes was transient, while repopulation by BM was permanent. These findings suggest that the isolated dLy-1 thymocytes described herein are precursor thymocytes that represent a very early stage in intrathymic development.