Skewed T cell receptor repertoire of Vδ1+ γδ T lymphocytes after human allogeneic haematopoietic stem cell transplantation and the potential role for Epstein-Barr virus-infected B cells in clonal restriction

The proliferation of V delta 1(+) gamma delta T lymphocytes has been described in various infections including human immunodeficiency virus (HIV), cytomegalovirus (CMV) and malaria. However, the antigen specificity and functions of the human V delta 1(+) T cells remain obscure. We sought to explore the biological role for this T cell subset by investigating the reconstitution of T cell receptor (TCR) repertoires of V delta 1(+) gamma delta T lymphocytes after human allogeneic haematopoietic stem cell transplantation (HSCT). We observed skewed TCR repertoires of the V delta 1(+) T cells in 27 of 44 post-transplant patients. Only one patient developed EBV-associated post-transplant lymphoproliferative disorder in the present patient cohort. The -WGI- amino acid motif was observed in CDR3 of clonally expanded V delta 1(+) T cells in half the patients. A skew was also detected in certain healthy donors, and the V delta 1(+) T cell clone derived from the donor mature T cell pool persisted in the recipient's blood even 10 years after transplant. This T cell clone expanded in vitro against stimulation with autologous EBV-lymphoblastoid cell lines (LCL), and the V delta 1(+) T cell line expanded in vitro from the same patient showed cytotoxicity against autologous EBV-LCL. EBV-infected cells could also induce in vitro oligoclonal expansions of autologous V delta 1(+) T cells from healthy EBV-seropositive individuals. These results suggest that human V delta 1(+) T cells have a TCR repertoire against EBV-infected B cells and may play a role in protecting recipients of allogeneic HSCT from EBV-associated disease.