Induction of Recipient Cell-Specific Donor T Cell Anergy by UV-C-Irradiated Recipient Immature Monocyte-Derived Dendritic Cells.

The induction of donor T cell anergy to recipient cells for reducing GVHD could be one way of expanding donor candidates for HLA-mismatched hematopoietic stem cell transplantation. The present study was designed to clarify whether recipient cell-specific T cell anergy could be induced by priming donor lymphocytes with recipient monocyte-derived dendritic cells (mo-DCs) irradiated with UV-C. By irradiation of mo-DCs with 100 J/m² or more UV-C, the expression of DC-associated surface phenotypes such as CD1a, CD54, CD40, CD80, CD83 and CD86 was reduced in one day after irradiation and the effects of UV-C irradiation continued for at least 7 days. By irradiation of mo-DCs with 100 J/m² or more UV-C, the antigen-presenting ability of both immature and mature mo-DCs, which was examined by ³H-thymidine incorporation assay, was clearly decreased at UV-C dose-dependent manner. Proliferation of CSFE-labeled lymphocytes by the stimulation with immature or mature Mo-DCs was suppressed by 300 J/m² UV-C irradiation to immature or mature mo-DCs. The response of normal donor 1 lymphocytes, which had been co-cultured with 300–3,000 J/m² UV-C-irradiated donor 2 immature mo-DCs for 7 days, against mature donor 2 mo-DCs in mixed leukocyte culture (MLC) for 7 days was markedly reduced, compared with the response of the donor 1 lymphocytes co-cultured with non-irradiated donor 2 mo-DCs or UV-C-irradiated mo-DCs derived from a different individual donor 3. CFSE-labeling analysis of donor 1 lymphocytes, which were co-cultured with 300 J/m² UV-C irradiated donor 2 mo-DCs in the first MLC and then stimulated with donor 2 mature mo-DCs in the second MLC, showed that by stimulation with mature mo-DCs in the second MLC, the proliferation of donor 1 lymphocytes co-cultured with UV-C irradiated donor 2 mo-DCs in the first MLC was less than that of the lymphocytes co-cultured with non-irradiated mature mo-DCs. Flow cytometry analysis of the lymphocytes co-cultured with 300 J/m² UV-C irradiated mo-DCs using surface CD4/CD25 and cytoplasmic Foxp3 monoclonal antibodies revealed that there was no increase of regulatory T cell population in the lymphocytes co-cultured with UV-C-irradiated immature mo-DCs, compared with the lymphocytes co-cultured with non-irradiated immature mo-DCs. Cell proliferation in allogeneic MLC consisting of lymphocytes as responder cells and mature mo-DCs as stimulator cells was not suppressed by the addition of the lymphocytes co-cultured with UV-C-irradiated immature mo-DCs. The present study demonstrated that recipient cell-specific T cell anergy could be induced by priming donor lymphocytes with UV-C-irradiated immature mo-DCs derived from a recipient and the T cell anergy was not associated with regulatory T cells. These data suggest the applicability of donor graft cells, which have been pre-stimulated with UV-C-irradiated recipient immature mo-DCs for expanding donor candidates for HLA-mismatched hematopoietic stem cell transplantation.