Enhanced susceptibility to apoptosis in T cells recovering after autologous peripheral blood progenitor cell transplantation: reversal by interleukin-15

Immune restoration following hematopoietic stem cell transplantation: an evolving target

Hematopoietic stem cell transplantation (HSCT) is the definitive cure for many malignant and nonmalignant diseases. However, delays in immune reconstitution (IR) following HSCT significantly limit the success of transplantation and increase the risk for infection and disease relapse in the transplant recipient. Therefore, ways to measure and to manipulate immune recovery following HSCT are emerging and their success depends directly upon an enhanced understanding for the underlying mechanisms responsible for reconstituted immunity and hematopoiesis. Recent discoveries in the activation, function, and regulation of dendritic cell (DC), natural killer (NK) cell, and T-lymphocyte subtypes have been critical in developing immunotherapies used to prevent graft-versus-host disease and to enhance graft-versus-leukemia. For example, regulatory T cells that induce tolerance and NK receptor-tumor ligand disparities that result in tumor lysis are being used to minimize GVHD and tumor burden, respectively. Furthermore, expansion and modulation of immune effector cells are being used to augment hematopoietic and immune recovery and to decrease transplant-related toxicity in the transplant recipient. Specifically, DC expansion and incorporation into antitumor and anti-microbial vaccines is fast approaching application into clinical trials. This paper will review our current understanding for IR following HSCT and the novel ways in which to restore immune function and decrease transplant-related toxicity in the transplant recipient.

Effect of interleukin-15 on anti-CD3/anti-CD28 induced apoptosis of umbilical cord blood CD4+ T cells

OBJECTIVES

Interleukin-15 (IL-15) has potential therapeutic advantage for patients receiving umbilical cord blood (CB) transplantation. The present study aims to examine the ability of IL-15 to modulate the survival, maturation, and function of anti-CD3/anti-CD28 stimulated CB CD4+ T cells, in comparison with responses from adult peripheral blood (APB) CD4+ T cells.

METHODS

Enriched CB and APB CD4+ T cells were stimulated with anti-CD3 and anti-CD28 (anti-CD3/anti-CD28) in the presence or absence of IL-15 (10 ng/mL) for 5 d. The percentages of apoptotic cells were assessed by propidium iodide/annexin-V flow cytometric staining. T-cell activation was analyzed with the expression of surface markers (CD45RO/CD69/CD25). Interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) production in culture supernatant was determined by enzyme-linked immunosorbent assay.

RESULTS

CB CD4+ T cells had a higher survival and lower apoptotic response following anti-CD3/anti-CD28 stimulation, compared with APB CD4+ T cells. IL-15 enhanced apoptosis and promoted CD45RO conversion of anti-CD3/anti-CD28 activated CB CD4+ T cells, an effect not observed with APB CD4+ T cells. Although activated CB CD4+ T cells expressed comparable level of CD69/CD25 expression to adults, IFN-gamma production of activated CB CD4+ T cells was markedly deficient compared with that of corresponding APB CD4+ T cells. Exogenous IL-15 further enhanced the production of IFN-gamma, but not TNF-alpha, of activated CB CD4+ T cells.

CONCLUSIONS

IL-15 preferentially resulted in an activation-enhancing effect on CB CD4+ T cells, accompanied by increased apoptosis. Our finding may have therapeutic implications while designing IL-15 immunotherapy for patients receiving CB transplant.

The role of growth factor administration and T-cell recovery after peripheral blood progenitor cell transplantation in the treatment of solid tumors: results from a randomized comparison of G-CSF and GM-CSF

BACKGROUND

Peripheral blood progenitor cell (PBPC) transplantation (PBPCT) combined with post-PBPCT administration of myelopoietic growth factors is a valid therapeutic intervention to rapidly restore hematopoiesis after the delivery of intensive, myeloablative cancer chemotherapy. On the other hand, the best growth factor regimen to potentiate PBPC-mediated immunohematopoietic recovery has yet to be determined.

STUDY DESIGN AND METHODS

In a randomized evaluation, the effects produced by post-PBPCT G-CSF and GM-CSF on myeloid/lymphoid recovery and transplant outcome in women with chemosensitive cancer were compared. Thirty-seven ovarian cancer patients and 34 breast cancer patients ranging in age from 24 to 60 years were treated with carboplatin, etoposide, and melphalan (CEM) high-dose chemotherapy and then randomly assigned to receive G-CSF (5 microg/kg subcutaneously) or GM-CSF (5 microg/kg subcutaneously) until Day 13 after PBPCT. Patients were compared in regard to hematopoietic recovery, posttransplant clinical management, and immune recovery. Finally, clinical outcome was estimated as time to progression and overall survival.

RESULTS

Hematopoietic recovery and posttransplant clinical management were comparable in both the G-CSF and GM-CSF series. Conversely, significantly higher T-cell counts were observed in G-CSF-treated patients during the early and late posttransplant follow-up. Patients who received G-CSF showed a significantly longer median time to progression. A parallel analysis revealed that patients in whom a higher CD3+ count was recovered had a significantly longer overall survival and time to progression.

CONCLUSION

The enhancement of post-PBPCT T-cell recovery observed in G-CSF-treated patients encourages the use of G-CSF to ameliorate immune recovery, which seems to play a role in post-PBPCT control of disease in cancer patients. GM-CSF might be administered to prolong immunosuppression after autologous PBPCT for autoimmune diseases or allogeneic PBPCT.