Ki Ryang Koh

Ex vivo expansion of mature human neutrophils with normal functions from purified peripheral blood CD34+ haematopoietic progenitor cells.

Purified CD34+ haematopoietic progenitor cells were cultivated with stem cell factor, interleukin 3 (IL‐3), granulocyte–macrophage colony‐stimulating factor (GM‐CSF) and granulocyte CSF (G‐CSF) for 7u2003d, and thereafter non‐adherent cells were divided into two groups. Cells in one group (group A) were further cultivated for 7u2003d with four cytokines, and cells in the other group (group B) were further cultivated for 7u2003d with G‐CSF alone. On day 14, 220‐fold and 130‐fold increases in the numbers of non‐adherent cells were achieved for groups A and B respectively. These cell preparations contained 65% granulocytes for group A and 95% granulocytes for group B. These cells gained the ability to respond effectively with chemotaxis, phagocytosis and superoxide (O2−) release. Cells in group B were appropriately primed by G‐CSF, GM‐CSF, tumour necrosis factor α and IL‐1β for enhanced release of . The responsiveness of these cells was identical to that of peripheral blood neutrophils, indicating that cells in group B may be in the resting state. In contrast, cells in group A were not primed by these cytokines for enhanced release of O2− and released a large amount of O2− spontaneously, indicating that cells in group A may be in the activated state. These findings indicate that mature neutrophils with normal functions were expanded ex vivo in group B and suggest that these cells could be used for possible autologous neutrophil transfusion to prevent bacterial infections during severe neutropenia after cytotoxic chemotherapy.

Potential Contribution of a Novel Tax Epitope–Specific CD4+ T Cells to Graft-versus-Tax Effect in Adult T Cell Leukemia Patients after Allogeneic Hematopoietic Stem Cell Transplantation

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an effective treatment for adult T cell leukemia/lymphoma (ATL) caused by human T cell leukemia virus type 1 (HTLV-1). We previously reported that Tax-specific CD8+ cytotoxic T lymphocyte (CTL) contributed to graft-versus-ATL effects in ATL patients after allo-HSCT. However, the role of HTLV-1–specific CD4+ T cells in the effects remains unclear. In this study, we showed that Tax-specific CD4+ as well as CD8+ T cell responses were induced in some ATL patients following allo-HSCT. To further analyze HTLV-1–specific CD4+ T cell responses, we identified a novel HLA-DRB1*0101–restricted epitope, Tax155–167, recognized by HTLV-1–specific CD4+ Th1-like cells, a major population of HTLV-1–specific CD4+ T cell line, which was established from an ATL patient at 180 d after allo-HSCT from an unrelated seronegative donor by in vitro stimulation with HTLV-1–infected cells from the same patient. Costimulation of PBMCs with both the identified epitope (Tax155–167) and known CTL epitope peptides markedly enhanced the expansion of Tax-specific CD8+ T cells in PBMCs compared with stimulation with CTL epitope peptide alone in all three HLA-DRB1*0101+ patients post–allo-HSCT tested. In addition, direct detection using newly generated HLA-DRB1*0101/Tax155–167 tetramers revealed that Tax155–167-specific CD4+ T cells were present in all HTLV-1–infected individuals tested, regardless of HSCT. These results suggest that Tax155–167 may be the dominant epitope recognized by HTLV-1–specific CD4+ T cells in HLA-DRB1*0101+–infected individuals and that Tax-specific CD4+ T cells may augment the graft-versus-Tax effects via efficient induction of Tax-specific CD8+ T cell responses.