Biomedical subjects

Christine Canning

Publications and source records attributed to Christine Canning.

9 recordsLinked to original sources

PubMed2006

IL-2 regulates FOXP3 expression in human CD4+CD25+ regulatory T cells through a STAT-dependent mechanism and induces the expansion of these cells in vivo.

IL-2 plays a critical role in the maintenance of CD4+CD25+ FOXP3(+) regulatory T cells (Tregs) in vivo. We examined the effects of IL-2 signaling in human Tregs. In vitro, IL-2 selectively up-regulated the expression of FOXP3 in purified CD4+CD25+ T cells but not in CD4+CD25- cells. This regulation involved the binding of STAT3 and STAT5 proteins to a highly conserved STAT-binding site located in the first intron of the FOXP3 gene. We also examined the effects of low-dose IL-2 treatment in 12 patients with metastatic cancer and 9 patients with chronic myelogenous leukemia after allogeneic hematopoietic stem cell transplantation. Overall, IL-2 treatment resulted in a 1.9 median fold increase in the frequency of CD4+CD25+ cells in peripheral blood as well as a 9.7 median fold increase in FOXP3 expression in CD3+ T cells. CD56+CD3- natural killer (NK) cells also expanded during IL-2 therapy but did not express FOXP3. In vitro treatment of NK cells with 5-aza-2'-deoxycytidine restored the IL-2 signaling pathway leading to FOXP3 expression, suggesting that this gene was constitutively repressed by DNA methylation in these cells. Our findings support the clinical evaluation of low-dose IL-2 to selectively modulate CD4+CD25+ Tregs and increase expression of FOXP3 in vivo.

Antigens, CD↗

PubMed2005

Graft-versus-tumor response in patients with multiple myeloma is associated with antibody response to BCMA, a plasma-cell membrane receptor.

Donor lymphocyte infusions (DLIs) induce effective graft-versus-tumor responses in patients with multiple myeloma who relapse after allogeneic hematopoietic stem-cell transplantation. The graft-versus-myeloma response is presumably mediated primarily by donor T cells, but recent studies have also demonstrated the presence of antibodies specific for a variety of myeloma-associated antigens in patients who achieve complete remission after DLI. One of the B-cell antigens identified in these studies was B-cell maturation antigen (BCMA), a transmembrane receptor of the tumor necrosis factor (TNF) superfamily that is selectively expressed by mature B cells. The present studies were undertaken to characterize the functional significance of antibodies to BCMA in vivo. Using transfected cells expressing BCMA, antibodies in patient serum were found to react with the cell-surface domain of BCMA. Post-DLI patient serum was able to induce complement-mediated lysis and antibody-dependent cellular cytotoxicity (ADCC) of transfected cells and primary myeloma cells expressing BCMA. BCMA antibodies were only found in post-DLI responders and not in other allogeneic transplant patients or healthy donors. These results demonstrate that BCMA is a target of donor B-cell immunity in patients with myeloma who respond to DLI. Antibody responses to cell-surface BCMA may contribute directly to tumor rejection in vivo.

Adult↗

PubMed2005

How PAs live and work.

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Attitude of Health Personnel↗

PubMed2003

Expansion of tumor-specific CD8+ T cell clones in patients with relapsed myeloma after donor lymphocyte infusion.

Donor lymphocyte infusions (DLI) provide effective therapy for patients with multiple myeloma who have relapsed after allogeneic bone marrow transplantation. However, the immunological mechanisms of the graft-versus-myeloma (GVM) effect have not been defined, and the target antigens of this response have not been identified. Molecular analysis of CDR3 Vbeta repertoire after CD4+ DLI demonstrated previously that the development of GVM and graft-versus-host-disease (GVHD) were associated with the clonal expansion of distinct T-cell populations in patient peripheral blood. In the current study, we undertook a molecular and functional characterization of GVM- and GVHD-associated T-cell clones. T-cell clones associated with GVM were detectable by clone-specific PCR at a low level in peripheral blood before DLI and expanded approximately 10-fold after DLI. In contrast, T-cell clones associated with GVHD were not detectable before DLI or before the development of clinical GVHD. Two T-cell clones associated with GVM were isolated and expanded in vitro, allowing their phenotypic and functional characterization. Both GVM clones were derived from donor cells and had a CD3+CD8+CD4- phenotype. One GVM clone specifically recognized patient myeloma cells in an HLA class I-restricted manner, but was not reactive with patient normal bone marrow cells or patient EBV transformed B cells. Taken together, these findings suggest that the GVM response is mediated by donor-derived CD8+ T-cell clones with antimyeloma specificity that may be present before DLI. In contrast, T-cell clones associated with GVHD are expanded de novo after DLI.

Adult↗

PubMed2002

CML28 is a broadly immunogenic antigen, which is overexpressed in tumor cells.

Donor lymphocyte infusion (DLI) reliably induces durable remission in 75-80% of patients with relapsed chronic myelogenous leukemia (CML) after allogeneic hematopoietic stem cell transplantation. To identify immunological targets of the graft-versus-leukemia response (GVL) after DLI, we used CML post-DLI responder sera to screen a CML cDNA expression library. One of the antigens identified in this screen is a M(r) 28,000 protein, termed CML28. CML28 is identical to hRrp46p, a component of the human exosome, a multiprotein complex involved in the 3' processing of RNA. Components of the human exosome include known autoantigens, such as PMScl-100, an autoantibody target in patients with polymyositis, scleroderma, or polymyositis-scleroderma overlap syndrome. Recombinant CML28-GST fusion protein was purified, and used in Western blot and ELISA to demonstrate the development of a high-titer CML28-specific IgG antibody response in a patient with relapsed CML who responded to DLI. Northern blotting demonstrated that CML28 is highly expressed in a variety of hematopoietic and epithelial tumor cell lines, but not in normal hematopoietic tissues or other normal tissue, with the exception of testis. Purified recombinant CML28 was used to generate a CML28-specific murine monoclonal antibody. Western blotting with CML28 monoclonal antibody against whole-cell lysates derived from blood and marrow of normal donors and patients with leukemia revealed high expression of this antigen in tumor but not in normal samples. Because CML28 was highly expressed in epithelial tumor cell lines, anti-CML28 responses were also examined in patients with solid tumors. By ELISA, we found specific serological responses in 10-33% of patients with lung cancer, melanoma, and prostate cancer. Our studies suggest that immunogenicity of CML28 is likely because of overexpression of this antigen in tumor cells. Moreover, given its expression and immunogenicity in a wide variety of malignancies, CML28 merits additional evaluation as a target for antigen-specific immunotherapy.

Antibodies, Neoplasm↗

PubMed2002

Immunologic effects of prophylactic donor lymphocyte infusion after allogeneic marrow transplantation for multiple myeloma.

Reconstitution of T-cell immunity after bone marrow transplantation (BMT) is often delayed, resulting in a prolonged period of immunodeficiency. Donor lymphocyte infusion (DLI) has been used to enhance graft-versus-leukemia activity after BMT, but the effects of DLI on immune reconstitution have not been established. We studied 9 patients with multiple myeloma who received myeloablative therapy and T-cell-depleted allogeneic BMT followed 6 months later by infusion of lymphocytes from the same donor. DLI consisted of 3 x 10(7) CD4(+) donor T cells per kilogram obtained after in vitro depletion of CD8(+) cells. Cell surface phenotype of peripheral lymphocytes, T-cell receptor (TCR) V beta repertoire, TCR rearrangement excision circles (TRECs), and hematopoietic chimerism were studied in the first 6 months after BMT and for 1 year after DLI. These studies were also performed in 7 patients who received similar myeloablative therapy and BMT but without DLI. Phenotypic reconstitution of T and natural killer cells was similar in both groups, but patients who received CD4(+) DLI developed increased numbers of CD20(+) B cells. TCR V beta repertoire complexity was decreased at 3 and 6 months after BMT but improved more rapidly in patients who received DLI (P =.01). CD4(+) DLI was also associated with increased numbers of TRECs in CD3(+) T cells (P <.001) and with conversion to complete donor hematopoiesis (P =.05). These results provide evidence that prophylactic infusion of CD4(+) donor lymphocytes 6 months after BMT enhances reconstitution of donor T cells and conversion to donor hematopoiesis as well as promoting antitumor immunity.

Adult↗

PubMed2002

Combination immunotherapy with rituximab and interleukin 2 in patients with relapsed or refractory follicular non-Hodgkin's lymphoma.

Rituximab has significant activity as a single agent in the treatment of follicular non-Hodgkin's lymphoma (NHL). Interleukin 2 (IL-2) is a lymphokine that increases effector cell number. In an effort to augment antibody-dependent cell-mediated cytotoxicity (ADCC) associated with rituximab therapy, low-dose IL-2 was added to a standard rituximab regimen and patients were evaluated for safety and efficacy. Twenty patients with relapsed or refractory follicular NHL were treated with IL-2 (1.2 MIU/m(2)/d for 56 d subcutaneously) as outpatients. Rituximab (375 mg/m(2)) was given on d 15, 22, 29 and 36. The regimen was well tolerated and only three patients required dose adjustments in IL-2. Infusional toxicity associated with rituximab was not exacerbated by IL-2. Peripheral blood immunophenotyping demonstrated significant increases in circulating CD8+ and CD56+ lymphocytes in all evaluable patients (P = 0.0002). Increases in total eosinophil number were observed in all patients. Eleven patients responded to therapy, for an overall response rate of 55%. Four additional patients had stable disease. For these 15 patients, the median time to progression exceeded 13 months. We conclude concomitant cytokine therapy to enhance ADCC with monoclonal antibody therapy was well tolerated and did not exacerbate antibody-related infusional toxicity. Further studies of this rational combination are warranted and ongoing.

Adult↗

PubMed2002

Randomized trial of CD8+ T-cell depletion in the prevention of graft-versus-host disease associated with donor lymphocyte infusion.

The application of DLI is limited by the potential development of GVHD. Results of single-arm trials suggest that CD8+ depletion of DLI may reduce the incidence of GVHD while still inducing pathologic and cytogenetic remissions. To test the impact of CD8 depletion on GVHD, we initiated a randomized trial comparing outcome among patients receiving unselected donor lymphocytes or CD8+-depleted cells. DLI was administered to patients with disease in remission to prevent relapse 6 months after T-cell-depleted allogeneic BMT. CD8 depletion was performed with monoclonal antibody and rabbit complement. Donor lymphocytes obtained from the original donor were infused fresh without cryopreservation. Infusions were adjusted so that all patients received 1.0 x 10(7) CD4+ cells/kg. Patients randomized to CD8 depletion received a median of 0.7 x 10(5) versus 32.0 x 10(5) CD8+ cells/kg in the unmanipulated cohort. Six (67%) of 9 patients receiving unselected DLI developed acute GVHD compared with 0 (0%) of 9 recipients of CD8-depleted DLI (P = .009). In the unselected group, 2 patients died while the disease was in remission, and 3 patients had relapses. In the CD8-depleted cohort, there were no toxic deaths and only 1 relapse. Measures of immunologic reconstitution by T-cell receptor excision circle analysis and T-cell receptor spectratyping demonstrated similar patterns of T-cell recovery in both the CD8-depleted and the unselected cohorts. Both groups converted from mixed to full donor hematopoietic chimerism after DLI. Our results indicate that CD8 depletion reduces the incidence of GVHD associated with DLI without adversely affecting conversion to donor hematopoiesis or immunologic recovery.

Bone Marrow Transplantation↗

PubMed2002

Infusion of CD4+ donor lymphocytes induces the expansion of CD8+ donor T cells with cytolytic activity directed against recipient hematopoietic cells.

PURPOSE: Donor lymphocyte infusions (DLIs) provide effectivetherapy for patients with relapsed chronic myeloid leukemia after allogeneic bone marrow transplantation. Previous studies have suggested that depletion of CD8+ T cells from the infused donor lymphocytes can reduce the incidence of graft-versus-host disease associated with DLI without reducing antileukemia activity. In this situation however, the immune effector cells responsible for tumor rejection have not been identified. The goal of this study was to characterize these effector populations. EXPERIMENTAL DESIGN: We studied three representative patients with relapsed chronic myeloid leukemia who achieved complete molecular remission after receiving CD8+ T-cell-depleted DLI from HLA-identical sibling donors. Effector T cells were characterized in patient samples after in vitro stimulation and functional assessment. T-cell clones relevant to the immune response were then isolated and further characterized. RESULTS: Analysis of peripheral blood samples collected after DLI indicated the presence of a high frequency of circulating host-reactive cytolytic CD8+ T cells secreting IFN-gamma. These HLA class I-restricted CTLs were specific for recipient minor histocompatibility antigens (mHAs) because they did not recognize target cells of donor origin. One CTL clone was further expanded in vitro and shown to recognize a broadly expressed mHA presented by HLA-B5701. Using a molecular approach, we demonstrated that this clone was expanded in peripheral blood and marrow after DLI. It was not detected before DLI. CONCLUSIONS: These results indicate that CD4+ DLI elicits a potent allogeneic response mediated by mHA-specific CD8+ T cells.

Adult↗