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Biomedical subjects

P McFadden

Publications and source records attributed to P McFadden.

8 recordsLinked to original sources
PubMed1996

A new limiting dilution culture system for the detection of T cell subsets in T cell-depleted marrow grafts.

T cell depletion (TCD) has been achieved using techniques that cause the inactivation, lysis, or physical removal of T cells from the donor marrow. The clinical results of TCD reflect, in part, the degree of TCD achieved and the subsets that are removed. To better evaluate TCD using the monoclonal antibody (mAb) T10B9, we have performed a series of flow cytometry and mAb blocking studies and have developed a new limiting dilution assay (LDA) that allows the detection of T cell subsets that survive treatment. T cell growth was stimulated with PHA, rIL-2, and irradiated feeder PBMC in a total well volume of 20 microliters. Growth was scored by microscopic examination on days 14-16 of incubation. Immunomagnetic beads coated with mAb were added to the growing wells and incubated, then the plates were fixed to a template of samarium cobalt magnets before washing away nonadherent cells. Wells in which > 50 cells bound > or = 2 beads were scored as positive. Flow cytometry indicated that T10B9 recognized all T cells, but complement-mediated lysis spared a significant proportion of the TCR gamma delta + subset. The epitope recognized by T10B9 on TCR gamma delta + cells appears to be differentially expressed compared with TCR alpha beta + T cells based on antibody blocking studies. In contrast to antibodies to CD3 epsilon, T10B9 binds less well to TCR gamma delta + cells, possibly resulting in incomplete complement-mediated lysis of this subset. The relative sparing of TCR gamma delta + cells was found in marrow and peripheral blood. Subset LDA confirmed that the TCR gamma delta + cells detected by flow cytometry were capable of growth and further showed that OKT3 did not spare TCR gamma delta + cells. The subset LDA should prove useful in helping to assess the role of T cell subsets in clinical events post-TCD bone marrow transplantation.

Bone Marrow Transplantation↗
PubMed1995

Characterization of the alloreactivity and anti-leukemia reactivity of cord blood mononuclear cells.

It has been suggested that cord blood T cells may be less able to mediate GVHD than marrow-derived T cells due to their naive status. A decreased potential for GVHD may be advantageous for allogeneic transplant, but this benefit might be counteracted by loss of the GVHD associated graft-versus-leukemia (GVL) effect. The GVL potential of cord blood could be doubly compromised since cord blood NK cell activity is also decreased. To assess these issues we have performed extensive comparative functional and immunophenotypic evaluations of cord and adult mononuclear cells. We found a somewhat reduced alloproliferative, allostimulatory and allocytolytic capacity of cord blood mononuclear cells in bulk assays but not by limiting dilution assays. Immunophenotyping revealed no significant differences in the proportion of major lymphocyte subsets with the exception of the previously recognized predominance of CD45RA+ cells in both CD4 and CD8 cord blood T cells. Cord blood T cells expressed normal percentages of the cellular adhesion molecules, CD11a, CD18 and LFA-3; however, the antigen density of each of these molecules was less than that found on adult T cells. Fewer resting cord blood T cells expressed CD54, the ligand for LFA-1. Cord blood B cells and monocytes expressed normal levels of HLA-class I and HLA class II DR, DP and DQ antigens, suggesting that the decreased expression of cellular adhesion molecules or their receptors rather than a decrease in expression of HLA might have contributed to the lower alloreactivity of cord blood. Although the percentages of NK cells and NK cell subsets in adult and cord blood were similar our data confirmed that cord blood has very low NK lytic activity. In contrast, LAK activity was much more readily induced in cord blood compared with adult PBMC, a finding which could be explained in part by a higher frequency of LAK precursors and a more rapid expansion of NK cells in response to culture with medium containing of NK cells in response to culture with medium containing IL-2. Cord blood LAK cells were readily able to lyse fresh leukemia targets from patients with ALL, AML and CML. The data indicate that although the alloreactive potential of cord blood cells may be somewhat decreased, it is not absent and must be considered a factor in cord blood transplants. LAKp with the potential to lyse leukemia are present in increased numbers in cord blood and might contribute to the GVL effect of a cord blood transplant.

Adult↗
PubMed1993

Salvage immunotherapy using donor leukocyte infusions as treatment for relapsed chronic myelogenous leukemia after allogeneic bone marrow transplantation: efficacy and toxicity of a defined T-cell dose.

Eight patients who had hematologic relapse of chronic myelogenous leukemia (CML) after undergoing allogeneic bone marrow transplantation (BMT) were treated with leukocyte infusions from the original bone marrow donors. All patients had previously received marrow grafts from HLA-identical siblings. Six patients were in the accelerated phase of their disease and two were in blast crisis. Each patient received a predetermined T-cell dose within a narrow range of 2.5 to 5.0 x 10(8) T cells/kg. Three patients also received short courses of therapy with alpha interferon to control elevated white blood cell counts within the first several weeks after leukocyte transfusions. Seven of eight evaluable patients developed graft-versus-host disease (GVHD) at a median of 32 days after the initial infusion. One patient had fatal GVHD. A second patient had grade 3 acute GVHD, which has responded to immunosuppressive therapy. The remaining patients all had mild grade I GVHD. Six patients continue to require modest doses of prednisone more than 6 months after infusion. Four patients developed marrow aplasia, which in three patients required marrow boosts from the original donors. Two of these three patients have normal hematopoietic function, whereas the third patient remains growth factor and transfusion dependent. Both patients treated in blast crisis have died, one from GVHD and one from disease progression. All six patients in the accelerated phase are alive and in cytogenetic remission at a median of 42 weeks after infusion. Five of these six patients are in molecular remission. This study demonstrates that leukocyte infusions that administered a defined T-cell dose can exert a profound graft-versus-leukemia effect and are an effective form of salvage immunotherapy in allogeneic marrow transplant recipients. This therapeutic approach appears to be a viable alternative to existing chemotherapeutic and immunomodulatory strategies for the treatment of relapsed CML.

Adult↗
PubMed1993

The ligamentization process: a 4 year case study following ACL reconstruction with a semitendinosis graft.

This study evaluates the histological and biochemical changes that occurred in a semitendinosis autograft 4 years after intraarticular placement as an anterior cruciate ligament (ACL) substitute in a human patient. The graft was harvested during total knee replacement. Comparison to harvested ACL and hamstring tendon was made. Changes in collagen crimp pattern, cell type, glycosaminoglycan composition, and collagen crosslinking were present between the ACL autograft and the hamstring tendon. The appearance and biochemical properties of the semitendinosis autograft and the native ACL were similar 4 years following intraarticular placement. These observed phenomena could be attributed to functional adaptation, supporting the concept of ligamentization.

Adaptation, Physiological↗