Oligoclonal expansion of CD4+CD28− T lymphocytes in recipients of allogeneic hematopoietic cell grafts and identification of the same T cell clones within both CD4+CD28+ and CD4+CD28− T cell subsets

Recipients of allogeneic bone marrow grafts have clonally expanded CD8+CD28− T lymphocytes during the early period after transplantation, which leads to skewing of T cell receptor (TCR) repertoires. Here, we have addressed the question of whether clonal expansion of CD28− T cells is also observed in CD4+ T lymphocytes after human allogeneic hematopoietic cell transplantation. We found that the fraction of T cells lacking CD28 expression in the CD4+ subset was increased after transplantation, and expanded CD4+CD28− T lymphocytes carrying certain TCRBV subfamilies showed limited TCR diversity. In order to further study the ontogeny of CD4+CD28− T cells, we analyzed the complementarity-determining region 3 (CDR3) of the TCR-β chain of CD4+CD28+ and CD4+CD28− cells. We identified the same T cell clones within both CD4+CD28− and CD4+CD28+ T cell subsets. These results suggest that both subsets are phenotypic variants of the same T cell lineage. Bone Marrow Transplantation (2001) 27, 1095–1100.