Differential effect of IL-15 and IL-2 on survival of phytohemagglutinin-activated umbilical cord blood T cells

IL2rg Cytokines Enhance Umbilical Cord Blood CD34+ Cells Differentiation to T Cells

PURPOSE

Umbilical cord blood (UCB) is an alternative source of hematopoietic stem cell (HSC) transplantation for the treatment of patients with leukemia if matched donor is not available. CD34+ is a pan marker for human hematopoietic stem cells, including umbilical cord blood stem cell. In comparison to other sources, cord blood CD34+ cells proliferate more rapidly and produce large number of progeny cells. For ex vivo expansion of Umbilical Cord Blood- HSCs/HPCs, different combinations of cytokines have been used in many laboratories. IL2rg cytokines, including IL2, IL7 and IL15, are key cytokines in the regulation of differentiation, proliferation and survival of immune cells. IL2 is important cytokine for T cell survival and proliferation, IL7 involve in B cell development and IL15 is a key cytokine for NK cell development. In this study we evaluated the generation of T cells derived from CD34+ and CD34- cord blood mononuclear cells by using combination of cytokines including IL2, IL7 and IL15.

METHODS

Cultured cord blood mononuclear cells were evaluated at distinct time points during 21 days by using flow cytometry.

RESULTS

Present study showed that differentiation of T cells derived from CD34+ cord blood mononuclear cells increased by using IL2 and IL7 at different time points. In the other hand IL15 did not show any significant role in generation of T cells from CD34+ cord blood mononuclear cells.

CONCLUSION

Taken together, our data illustrated that either IL2 or IL7 versus other cytokine combinations, generate more T cell from cord blood CD34 cells, probably this cytokines can be the best condition for ex vivo expansion of UCB HSCs.

Antigen-Specific Priming is Dispensable in Depletion of Apoptosis-Sensitive T Cells for GvHD Prophylaxis

Prophylactic approaches to graft versus host disease (GvHD) have employed both phenotypic reduction of T cells and selective elimination of host-primed donor T cells in vitro and in vivo. An additional approach to GvHD prophylaxis by functional depletion of apoptosis-sensitive donor T cells without host-specific sensitization ex vivo showed remarkable reduction in GHD incidence and severity. We address the role and significance of antigen-specific sensitization of donor T cells and discuss the mechanisms of functional T cell purging by apoptosis for GvHD prevention. Host-specific sensitization is dispensable because migration is antigen-independent and donor T cell sensitization is mediated by multiple and redundant mechanisms of presentation of major and minor histocompatibility complex and tissue antigens by donor and host antigen-presenting cells. Our data suggest that potential murine and human GvH effectors reside within subsets of preactivated T cells susceptible to negative regulation by apoptosis prior to encounter of and sensitization to specific antigens.

Umbilical cord blood immunology: relevance to stem cell transplantation

Because of its easier accessibility and less severe graft-versus-host disease, umbilical cord blood (UCB) has been increasingly used as an alternative to bone marrow for hematopoietic stem cell transplantation. Naiveté of UCB lymphocytes, however, results in delayed immune reconstitution and infection-related mortality in transplant recipients. This review updates the phenotypic and functional deficiencies of various immune cell populations in UCB compared with their adult counterparts and discusses clinical implications and possible therapeutic strategies to improve the outcome of stem cell transplantation.

Expansion of CD4(+)CD25 (+) regulatory T cells from cord blood CD4(+) cells using the common γ-chain cytokines (IL-2 and IL-15) and rapamycin

Rapamycin has important roles in the modulation of regulatory T cells. We tried to expand CD4(+)CD25(+) regulatory T cells (Treg cells) from umbilical cord blood (CB) CD4-positive cells using interleukin (IL)-15 or IL-2 with transforming growth factor (TGF)-β and rapamycin. We were able to obtain more than 500-fold expansion of CD4(+)CD25(+) cells from CB CD4(+) cells using IL-15 and TGF-β with rapamycin. These expanded CD4(+)CD25(+) cells expressed forkhead box P3 (FoxP3) mRNA at a level about 100-fold higher and could suppress allogeneic mixed lymphocyte culture (MLC) by more than 50%. Early after rapamycin stimulation, CB CD4(+) cells showed increased expression of FoxP3 and a serine/threonine kinase Pim2 and sustained expression of negative phosphoinositide 3-kinase regulator phosphatase and tensin homolog deleted on chromosome 10 (PTEN). On the other hand, CD4(+)CD25(+) cells expanded with rapamycin for 8 days showed much higher levels of FoxP3 mRNA expression and decreased expression of PTEN. A comparison of IL-15 stimulation and IL-2 stimulation showed slightly higher efficiency of IL-15 for expansion of CD4(+)CD25(+) cells, and for FoxP3 expression, IL-15 also showed significantly higher efficacy for inhibition of MLC. The combination of the common γ-chain cytokine IL-15, TGF-β, and rapamycin may be a useful means for expanding Treg cells. Pim2 expression early after stimulation with rapamycin may be important for conferring rapamycin resistance for growth of Treg cells. IL-15 is not less useful than IL-2 for expansion of Treg cells.

The regulatory function of umbilical cord blood CD4(+) CD25(+) T cells stimulated with anti-CD3/anti-CD28 and exogenous interleukin (IL)-2 or IL-15

The abundance of CD4(+) CD25(+) regulatory T cells in umbilical cord blood (UCB) might contribute to the decreased severity of graft-vs.-host disease (GVHD) for UCB transplantation. This study aims to characterize the phenotypes and suppressive function of UCB CD4(+) CD25(+) T cells under the influence of anti-CD3/anti-CD28 (CD3/CD28) and exogenous interleukin (IL)-2 or IL-15. Higher percentages of CD4(+) CD25(high) and FoxP3(+) cells were detected in UCB compared to their adult counterparts. IL-15 was as effective as IL-2 in enhancing the proliferation of CD3/CD28 stimulated UCB CD4(+) CD25(+) T cells. Phenotypically, IL-2/IL-15-stimulated UCB CD4(+) CD25(+) T cells expressed higher level of CTLA-4, GITR, membrane bound transforming growth factor-beta (mTGF-beta), and especially Foxp-3 than controls. IL-2/IL-15-stimulated UCB CD4(+) CD25(+) T cells also produced much higher IL-10 and TGF-beta than controls; while IL-2/IL-15-stimulated UCB CD4(+) CD25(-) T cells showed increased TGF-beta, but not IL-10 production. IL-2/IL-15-cultured UCB CD4(+) CD25(+) T cells showed comparable suppressor activity on allogeneic adult CD4(+) T-cell proliferation compared to controls, partly through a contact-dependent fashion. Taken together, IL-2/IL-15-stimulated UCB CD4(+) CD25(+) T cells show distinct regulatory T-cell phenotypic and functional features, and may be applied for the alleviation of GVHD severity following UCB transplantation.

Susceptibility to Fas and tumor necrosis factor-alpha receptor mediated apoptosis of anti-CD3/anti-CD28-activated umbilical cord blood T cells

Decreased severity of graft-versus-host disease after mismatched umbilical cord blood (UCB) transplantation may be attributed in part to the increased propensity to apoptosis of UCB T cells following activation. Interleukin (IL)-15, a pleiotropic cytokine that is essential for T-cell proliferation and survival, may serve as promising immunomodulative therapy post-CB transplantation for its anti-apoptotic effect. This study aimed to determine the kinetics of Fas or tumor necrosis factor-alpha receptor (TNFR) mediated caspase-3 expression and apoptosis of anti-CD3/anti-CD28 activated UCB T cells in the influence of IL-15. Activated caspase-3 expression was analyzed by Western blotting and the percentage of apoptotic cells was determined by annexin-V/propidium iodide (PI) flow cytometric staining. Significant expression of Fas and TNFR2 was detected on anti-CD3/anti-CD28 pre-activated UCB T cells. These cells were susceptible to anti-Fas but not TNF-alpha-induced apoptosis. Kinetic study shows that caspase-3 expression became evident at 6th-8th h following anti-Fas stimulation, while early apoptotic cells with annexin-V(+)/PI(-) expression appeared at 12th-16th h. IL-15, though successful in decreasing apoptosis in pre-activated UCB T cells, failed to completely prevent Fas-mediated caspase-3 expression and apoptosis of CB T cells. The pre-activated UCB and adult peripheral blood T cells behaved similarly with regard to death receptor expression, caspase-3 expression and apoptosis upon Fas-engagement. Although IL-15 promotes overall activated UCB T-cell survival, it did not particularly prevent Fas-mediated activation-induced cell death.

Co-immunization with IL-15 enhances cellular immune responses induced by a vif-deleted simian immunodeficiency virus proviral DNA vaccine and confers partial protection against vaginal challenge with SIVmac251

Simian immunodeficiency virus (SIV) infection of rhesus macaques is a valuable animal model for human immunodeficiency virus (HIV)-1 vaccine development. Our laboratory recently described the immunogenicity and limited efficacy of a vif-deleted SIVmac239 proviral DNA (SIV/CMVDelta vif) vaccine. The current report characterizes immunogenicity and efficacy for the SIV/CMVDelta vif proviral DNA vaccine when co-inoculated with an optimized rhesus interleukin (rIL)-15 expression plasmid. Macaques co-inoculated with rIL-15 and SIV/CMVDelta vif proviral plasmids showed significantly improved SIV-specific CD8 T cell immunity characterized by increased IFN-gamma ELISPOT and polyfunctional CD8 T cell responses. Furthermore, these animals demonstrated a sustained suppression of plasma virus loads after multiple low dose vaginal challenges with pathogenic SIVmac251. Importantly, SIV-specific cellular responses were greater in immunized animals compared to unvaccinated controls during the initial 12 weeks after challenge. Taken together, these findings support the use of IL-15 as an adjuvant in prophylactic anti-HIV vaccine strategies.

Role of interleukin-15 in umbilical cord blood transplantation

Owing to its easier accessibility and less severe graft-versus-host disease, umbilical cord blood (UCB) has been increasingly used as an alternative to bone marrow for hematopoietic stem-cell transplantation. Naiveté of UCB lymphocytes, however, results in delayed immune reconstitution and infection-related mortality in transplant recipients. This article reviews UCB immunology and addresses the potential therapeutic role of interleukin (IL)-15, a pleiotropic gamma chain signaling cytokine, in modulating immune reconstitution, graft-versus-host disease (GVHD), graft-versus-leukemia effect, and infection susceptibility during the post-UCB transplant period. Cytokine immunotherapy using IL-15 simultaneously modulates several immune compartments, thus holds promise for facilitating post-transplant recovery and augmenting antitumor effect without aggravating GVHD in the setting of UCB transplantation.

Differential cyclosporin-A sensitivity on survival and activation of umbilical cord and adult peripheral blood CD4+ T cells

Enhanced cyclosporine-A (CsA) sensitivity of umbilical cord blood (CB) CD4(+) T cells may contribute to the lower incidence of graft-versus-host disease (GVHD) after mismatched CB transplantation. Interleukin (IL)-15, an IL-2 like gamma-chain signaling cytokine, may bypass CsA inhibition and play an important role in GVHD pathogenesis. The present study examines CsA sensitivity of IL-15-driven CB CD4(+) T cell survival, activation and proliferation, comparing adult peripheral blood (APB) CD4(+) T cell responses. We establish that (1) resting CB CD4(+) T cells were more susceptible to CsA-induced cell death than their adult counterpart; (2) IL-15 help support the survival of resting CB CD4(+) T cell under the influence of CsA, though to a lesser degree that observed in adults; (3) higher CsA sensitivity of CD25 up-regulation following TCR activation was observed in CB but more readily counteracted by IL-15 compared to adults; (4) IL-15-driven proliferation of TCR-activated CD4(+) T cells was more susceptible to CsA inhibition than corresponding adults; and (5) TCR-activated CB CD4(+) T cells surviving high dose CsA (5 microg/ml) in IL-15-supplemented cultures expressed significantly lower percentages of CD45RO(-)/CD25(+) subsets compared to corresponding APB. Taken together, the differential CsA sensitivity and IL-15 response between CB and APB CD4(+) T cells may contribute to the lessened GVHD severity in the setting of CB transplantation.

Effect of interleukin-15 on alloreactivity in umbilical cord blood

Interleukin(IL)-15 is a promising immunotherapeutic agent for immune reconstitution following stem cell transplantation. To investigate whether IL-15 would aggravate graft-versus-host disease (GVHD) in the setting of unrelated umbilical cord blood (CB) transplantation, we examined the effect of IL-15 on activation marker expression, proliferation and cytokine production of CB in a one-way mixed lymphocyte culture (MLC) assay. We found that IL-15 differentially enhanced CD69 and CD25 expression on CB T cells following allo-stimulation. The maximum degree of allo-specific CB proliferation was achieved on Day 6. IL-15 down-regulated the CB alloreactive proliferative response on Days 4, 6, and 8, with preferentially enhanced autologous proliferation. Exogenous IL-15 further enhanced CB TNF-alpha and IL-10 production in both autologous and allogeneic MLC 6 days after allopriming. Thus, IL-15 was effective in enhancing activation marker expression and cytokine production during CB alloreactivity, but failed to enhance allospecific proliferation. Further studies would be needed to study the role of IL-15 on GVHD in the setting of CB transplantation.