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Background The presence of T and B cells in allogeneic grafts contributes to GvHD and to EBV-associated lymphoproliferative disease (LPD). Depletion of T and B cells from the graft decreases the risk of these complications. Methods T and B cells were depleted from mobilized peripheral stem cells from volunteer donors (n=5) using anti-CD3 and anti-CD19 Abs conjugated to magnetic microbeads, and the CliniMACS device. The function of the stem cells after depletion was evaluated using colony assays and non-obese diabetic (NOD)/SCID repopulating experiments. Results The mean mononuclear cell (MNC) count prior to T- and B-cell depletion was 2.19×10 10 (range 1.48-3.53). After depletion, the mean percentage of contaminating T cells was 0.02% (range 0.01-0.04%) with a mean log 10 depletion of 3.4 (range 3-3.8). The mean percentage of contaminating B cells was 0.1% (range 0.01-0.4%) with a mean log 10 depletion of 2.2 (range 1.4-3). The mean recovery of CD3- and CD19-negative MNCs after depletion was 70% (range 54-88%) and the mean recovery of CD34 + stem cells was 69% (range 52-98%). The mean number of natural killer (NK) cells after T- and B-cell depletion was 5.2×10 8 (range 2-10×10 8 ). In vitro colony assays and in vivo NOD/SCID repopulation assays showed no negative impact of this method on the function of the hematopoietic stem cells. Discussion Our results show that the CliniMACS system can be used to efficiently deplete PBSC of T and B cells simultaneously, without adverse effect on the graft. [ABSTRACT FROM AUTHOR]

Background Infection, graft failure, disease relapse, and GvHD are significant adverse events associated with allogeneic BMT. Although donor leukocyte infusion has been used to prevent or to treat infection, graft failure, and relapse, the potential clinical benefits are often outweighed by the risk of T cell-mediated GvHD. Results from animal studies suggest that donor natural killer (NK) cells may be an ideal cell type for prevention or treatment of these adverse events. We have therefore sought to develop an automated, efficient, and clinical-scale human NK cell-purification method. Methods Twelve leukopheresis products were purified for NK cells using a two-step immunomagnetic method. CD3 + cells were first depleted from the apheresis products. CD56 + cells were then enriched from the CD3 + cell-depleted products. Results The median percentage of CD3 - CD56 + NK cells in the final products was 91.0%, and the median recovery was 48.7%. The median depletion for CD3 + CD56 - T cells was 5.3 log. Natural cytotoxicity of the purified cells was approximately five-fold higher than that of unpurified mononuclear cells, and it could be further increased by stimulation of the purified cell with IL2. Discussion We described a large-scale purification method for automated, efficient, and rapid isolation of human NK cells that yielded minimal contamination with T cells or B cells. These purified NK cells may be expedient for preclinical and clinical uses. [ABSTRACT FROM AUTHOR]

Presents a study that investigated the feasibility and efficacy of large-scale T cell depletion from granulocyte colony-stimulating factor mobilized peripheral blood stem cells (PBSC). Importance of T cell depletion to graft engineering strategies; Sources of hematopoietic stem cells; Comparison between bone marrow and PBSC transplantation; Ways of preventing graft-versus-host disease.

Allogeneic bone marrow transplantation (BMT) is an effective therapy for a variety of malignancies and blood disorders, but rarely serves as a frontline treatment because of numerous, potential complications. Important and frequent complications relate to the profound immunosuppression that inevitably occurs during the first several months following treatment. To better elucidate and subsequently improve immune reconstitution, we examined T and B cell subsets among 43 pediatric BMT recipients in a retrospective study. We found that the relative numbers of T cells and B cells (T:B ratios) were discordant and highly variable among patients at day ∼100 after BMT. Further investigation of BMT parameters identified a strong correlation between T:B ratios and immunosuppressive drug treatments, providing an explanation for variable lymphocyte reconstitution profiles. Results suggest that: (1) immunosuppressive therapy inhibits B cell expansion more strongly than T cell expansion following BMT; (2) WBC and absolute lymphocyte counts fail to reveal profound B cell immunodeficiencies in some BMT patients; and (3) routine analyses of T:B ratios serve to identify patients warranting close follow-up and extended supportive immunotherapy. Bone Marrow Transplantation (2001) 28, 573–580. [ABSTRACT FROM AUTHOR]