Isolation of human CD4/CD8 double-positive, graft-versus-host disease-protective, minor histocompatibility antigen-specific regulatory T cells and of a novel HLA-DR7-restricted HY-specific CD4 clone.

Minor histocompatibility (H) Ags are classically described as self-peptides derived from intracellular proteins that are expressed at the cell surface by MHC class I and class II molecules and that induce T cell alloresponses. We have isolated three different T cell populations from a skin biopsy of a patient suffering from acute graft-versus-host disease following sex-mismatched HLA-identical bone marrow transplantation. The first population was: 1) CD4(+)/CD8(+) double-positive; 2) specific for an HLA class I-restricted autosomal Ag; 3) expressed a Tr1 profile with high levels of IL-10, but low IL-2 and IFN-γ; and 4) exerted regulatory function in the presence of recipient APCs. The second was CD8 positive, specific for an HLA class I-restricted autosomally encoded minor H Ag, but was only weakly cytotoxic. The third was CD4 single positive, specific for an HLA-DR7-restricted HY epitope and exerted both proliferative and cytotoxic functions. Identification of the peptide recognized by these latter cells revealed a new human HY epitope, TGKIINFIKFDTGNL, encoded by RPS4Y and restricted by HLA-DR7. In this paper, we show human CD4/CD8 double-positive, acute graft-versus-host disease-protective, minor H Ag-specific regulatory T cells and identify a novel HLA-DR7/ HY T cell epitope, encoded by RPS4Y, a potential new therapeutic target.

Minor histocompatibility antigen DDX3Y induces HLA-DQ5-restricted T cell responses with limited TCR-Vbeta usage both in vivo and in vitro.

In vitro stimulation of human female T cells with male HLA-identical dendritic cells resulted in the generation of HLA-DQB1*0501/0502-restricted minor histocompatibility H-Y antigen-specific CD4(+) T cell clones. Two clones generated from different HLA-identical pairs were analyzed. Use of HLA-DQ5-expressing female Epstein-Barr virus transformed B lymphoblastoid cell lines transfected with various H-Y genes and loaded with overlapping peptides demonstrated that both T cell clones are specific for a peptide encoded by DDX3Y. Previously, an HLA-DQ5-restricted T cell clone specific for the same peptide was isolated from a patient with graft-versus-host disease. Thus, we compared the T cell receptor (TCR) rearrangements of the 2 in vitro generated T cell clones and the ex vivo isolated T cell clone. All 3 clones shared the same TCRBV5-4* gene segment and 2 of 3 clones also used similar TCR-Valpha segments. Our results suggest that T cells recognizing the HLA-DQ5/DDX3Y T cell epitope might be characterized by a relatively limited TCR-beta repertoire. The differences in the junctional TCR-beta region had no effect on the antigen specificity, but altered the capacity of the TCR to distinguish the HLA-DQ5/DDX3Y complex from its allelic counterpart. The results also demonstrate that in vitro stimulation of T cells with allogeneic HLA-identical dendritic cells may facilitate the characterization of in vivo, potentially relevant HLA class II-restricted minor H epitopes.

Isolation of regulatory T cells in the skin of a human hand-allograft, up to six years posttransplantation.

BACKGROUND: A bilateral hand allotransplantation was performed in a patient six years ago. Whereas skin is known to be highly immunogenic, grafts have been well accepted up to now. Therefore, here we investigated the putative presence of regulatory T cells in the graft. METHODS: Skin biopsies were performed at different time points and analyzed by immunochemistry. T cells were initially expanded with interleukin (IL)-2. In the latter biopsy, skin was directly analyzed by reverse-transcriptase polymerase chain reaction without any culture. RESULTS: When tested against donor mononuclear cells, donor-primed skin T cells demonstrated unresponsiveness and inhibited donor-directed blood T cell alloresponse. Moreover, their T-cell receptor-Vbeta repertoire was skewed, in contrast to that of peripheral blood T cells. Retrospectively, nuclear FoxP3 expression in skin was measured by immunohistochemistry and was found positive at that time, but appeared to increase with time. This result was supported by the measurement of FoxP3 messenger RNA (mRNA) expression in the latter fresh biopsy, which showed higher levels than that of blood, together with no expression of perforin mRNA, but increased expression of transforming growth factor-beta and IL-10. No FoxP3 mRNA expression was found in the contralateral leg, due to the absence of T cell infiltrate. CONCLUSION: This study shows the presence of the FoxP3 marker, in a well accepted human composite tissue allograft, up to six years posttransplantation. Because a suppressive cytokinic profile was also detected intragraft, in the absence of perforin mRNA expression, our data suggest that regulatory T cells could play a role in the long-term survival of this allograft.