Donor γδ T Lymphocytes Promote Allogeneic Engraftment Across the Major Histocompatibility Barrier in Mice

γδ T cells in oral diseases

OBJECTIVE

γδ T cells are a distinct subset of unconventional T cells, which link innate and adaptive immunity by secreting cytokines and interacting with other immune cells, thereby modulating immune responses. As the first line of host defense, γδ T cells are essential for mucosal homeostasis and immune surveillance. When abnormally activated or impaired, γδ T cells can contribute to pathogenic processes. Accumulating evidence has revealed substantial impacts of γδ T cells on the pathogenesis of cancers, infections, and immune-inflammatory diseases. γδ T cells exhibit dual roles in cancers, promoting or inhibiting tumor growth, depending on their phenotypes and the clinical stage of cancers. During infections, γδ T cells exert high cytotoxic activity in infectious diseases, which is essential for combating bacterial and viral infections by recognizing foreign antigens and activating other immune cells. γδ T cells are also implicated in the onset and progression of immune-inflammatory diseases. However, the specific involvement and underlying mechanisms of γδ T cells in oral diseases have not been systematically discussed.

METHODS

We conducted a systematic literature review using the PubMed/MEDLINE databases to identify and analyze relevant literature on the roles of γδ T cells in oral diseases.

RESULTS

The literature review revealed that γδ T cells play a pivotal role in maintaining oral mucosal homeostasis and are involved in the pathogenesis of oral cancers, periodontal diseases, graft-versus-host disease (GVHD), oral lichen planus (OLP), and oral candidiasis. γδ T cells mainly influence various pathophysiological processes, such as anti-tumor activity, eradication of infection, and immune response regulation.

CONCLUSION

This review focuses on the involvement of γδ T cells in oral diseases, with a particular emphasis on the main functions and underlying mechanisms by which γδ T cells influence the pathogenesis and progression of these conditions. This review underscores the potential of γδ T cells as therapeutic targets in managing oral health issues.

Unrelated donor α/β T-cell and B-cell-depleted HSCT for the treatment of pediatric acute leukemia

URD HSCT with TCRαβ/CD19 depletion is a safe and effective approach to alternative donor transplantation for hematologic malignancies.

Nonpermissive mismatch at DP was associated with a 16.5-fold risk of acute GVHD and may represent a modifiable target to mitigate GVHD risk.

Unrelated donor (URD) hematopoietic stem cell transplant (HSCT) is associated with an increased risk of severe graft-versus-host disease (GVHD). TCRαβ/CD19 depletion may reduce this risk, whereas maintaining graft-versus-leukemia. Outcome data with TCRαβ/CD19 depletion generally describe haploidentical donors, with relatively few URDs. We hypothesized that TCRαβ/CD19-depletion would attenuate the risks of GVHD and relapse for URD HSCT. Sixty pediatric and young adult (YA) patients with hematologic malignancies who lacked a matched-related donor were enrolled at 2 large pediatric transplantation centers between October 2014 and September 2019. All patients with acute leukemia had minimal residual disease testing, and DP typing was available for 77%. All patients received myeloablative total body irradiation– or busulfan-based conditioning with no posttransplant immune suppression. Engraftment occurred in 98%. Four-year overall survival was 69% (95% confidence interval [CI], 52%-81%), and leukemia-free survival was 64% (95% CI, 48%-76%), with no difference between lymphoid and myeloid malignancies (P = .6297 and P = .5441, respectively). One patient (1.7%) experienced primary graft failure. Relapse occurred in 11 patients (3-year cumulative incidence, 21%; 95% CI, 11-34), and 8 patients (cumulative incidence, 15%; 95% CI, 6.7-26) experienced nonrelapse mortality. Grade III to IV acute GVHD was seen in 8 patients (13%), and 14 patients (26%) developed chronic GVHD, of which 6 (11%) had extensive disease. Nonpermissive DP mismatch was associated with higher likelihood of acute GVHD (odds ratio, 16.50; 95% CI, 1.67-163.42; P = .0166) but not with the development of chronic GVHD. URD TCRαβ/CD19-depleted peripheral HSCT is a safe and effective approach to transplantation for children/YAs with leukemia. This trial was registered at www.clinicaltrials.gov as #NCT02323867.

IL-17-producing γδT cells ameliorate intestinal acute graft-versus-host disease by recruitment of Gr-1+CD11b+ myeloid-derived suppressor cells

Acute graft-versus-host disease (aGVHD) is the most severe complication and the major cause of morbidity and mortality in patients who have received hematopoietic stem cell transplantation. Inflammation mediated by donor T cells and neighboring recipient cells is considered to be responsible for intestinal aGVHD. Interleukin (IL)-17A-producing γδT (γδT17) cells have been investigated as key players in cancer, immunity, and inflammatory responses because of their phenotypic plasticity, memory-like activity, and unique migratory features. However, the precise roles and underlying mechanisms of γδT17 cells in aGVHD immunopathogenesis remain elusive. Here, we found that γδT17 cells constituted the major resident γδT population in the intestinal lamina propria of aGVHD mice. Adoptive infusion of induced γδT17 cells markedly attenuated murine aGVHD and increased infiltration of Gr-1⁺CD11b⁺ myeloid-derived suppressor cells (MDSCs) into the inflammatory intestine, and did not affect graft-versus-leukemia(GVL) effect. Further experiments indicated that γδT17 cells enhanced both migration ability and immunosuppressive activity of MDSCs. γδT17 cell-mediated protection in aGVHD was blunted by depletion of IL-17A or MDSCs. Our study clarifies an immune pathway where γδT17 cells play a protective role in murine aGVHD by recruiting MDSCs to the inflammatory intestine.

Impact of γδ T cells on clinical outcome of hematopoietic stem cell transplantation: systematic review and meta-analysis

Allogeneic hematopoietic stem cell transplantation (HSCT) using αβ T-/B-cell-depleted grafts recently emerged as a transplant strategy and highlighted the potential role of γδ T cells on HSCT outcomes. Our aim was to scrutinize available evidence of γδ T-cell impact on relapse, infections, survival, and acute graft-versus-host disease (aGVHD). We performed a systematic review and meta-analysis of studies assessing γδ T cells in HSCT. We searched PubMed, Web of Science, Scopus, and conference abstracts from inception to March 2019 for relevant studies. We included all studies that assessed γδ T cells associated with HSCT. Data were extracted independently by 2 investigators based on strict selection criteria. A random-effects model was used to pool outcomes across studies. Primary outcome was disease relapse. We also assessed infections, survival, and aGVHD incidence. The review was registered with PROSPERO (CRD42019133344). Our search returned 2412 studies, of which 11 (919 patients) were eligible for meta-analysis. Median follow-up was 30 months (interquartile range, 22-32). High γδ T-cell values after HSCT were associated with less disease relapse (risk ratio [RR], 0.58; 95% confidence interval [95% CI], 0.40-0.84; P = .004; I2 = 0%), fewer viral infections (RR, 0.59; 95% CI, 0.43-0.82; P = .002; I2 = 0%) and higher overall (HR, 0.28; 95% CI, 0.18-0.44; P < .00001; I2 = 0%) and disease-free survivals (HR 0.29; 95% CI, 0.18-0.48; P < .00001; I2 = 0%). We found no association between high γδ T-cell values and aGVHD incidence (RR, 0.72; 95% CI, 0.41-1.27; P = .26; I2 = 0%). In conclusion, high γδ T cells after HSCT is associated with a favorable clinical outcome but not with aGVHD development, suggesting that γδ T cells have a significant effect on the success of HSCT. This study was registered with PROSPERO as #CRD42019133344.

Haploidentical HSCT for hemoglobinopathies: improved outcomes with TCRαβ+/CD19+-depleted grafts

We examined outcomes of haploidentical hematopoietic cell transplantation (haplo-HCT) using T-cell receptor αβ⁺ (TCRαβ⁺)/CD19⁺-depleted grafts (TCR group, 14 patients) in children with hemoglobinopathies. Patients received a preparative regimen consisting of busulfan, thiotepa, cyclophosphamide, and antithymocyte globulin preceded by fludarabine, hydroxyurea, and azathioprine. The median follow-up among surviving patients was 3.9 years. The 5-year probabilities of overall survival (OS) and disease-free survival (DFS) were 84% and 69%, respectively. The incidence of graft failure was 14%. We compared outcomes to a historical group of 40 patients with hemoglobinopathies who received CD34⁺-selected grafts (CD34 group). The median follow-up of surviving patients for the CD34 group was 7.5 years. The 5-year probabilities of OS and DFS were 78% and 39%, respectively. The CD34 group had a significantly higher incidence of graft failure (45%) than the TCR group (14%) (P = .048). The incidences of grades 2 to 4 acute graft-versus-host disease (GVHD) in the TCR and CD34 groups were 28% and 29%, respectively, and 21% and 10% (P = .1), respectively, for extensive chronic GVHD. Viral reactivation was common in both groups. The overall incidence of posttransplant lymphoproliferative disorders for the entire group was 16%. Among all patients, 5 developed autoimmune hemolytic anemia or thrombocytopenia, with the overall cumulative incidence of 11%. The 2 groups showed suboptimal CD4⁺ recovery within the first 6 months of transplantation with no significant difference between groups. These data demonstrate that TCRαβ⁺/CD19⁺-depleted grafts are associated with a reduced incidence of graft failure, but delayed immune reconstitution and associated morbidity and mortality remain a significant challenge.

Deciphering the Contribution of γδ T Cells to Outcomes in Transplantation

γδ T cells are a subpopulation of lymphocytes expressing heterodimeric T-cell receptors composed of γ and δ chains. They are morphologically and functionally heterogeneous, innate yet also adaptive in behavior, and exhibit diverse activities spanning immunosurveillance, immunomodulation, and direct cytotoxicity. The specific responses of γδ T cells to allografts are yet to be fully elucidated with evidence of both detrimental and tolerogenic roles in different settings. Here we present an overview of γδ T-cell literature, consider ways in which their functional heterogeneity contributes to the outcomes after transplantation, and reflect on methods to harness their beneficial properties.

Role of αβ T Cell Depletion in Prevention of Graft versus Host Disease

Graft versus host disease (GVHD) represents a major complication of allogeneic hematopoietic stem cell transplantation (allo HCT). Graft cellular manipulation has been used to mitigate the risk of GVHD. The αβ T cells are considered the primary culprit for causing GVHD therefore depletion of this T cell subset emerged as a promising cellular manipulation strategy to overcome the human leukocyte antigen (HLA) barrier of haploidentical (haplo) HCT. This approach is also being investigated in HLA-matched HCT. In several studies, αβ T cell depletion HCT has been performed without pharmacologic GVHD prophylaxis, thus unleashing favorable effect of donor’s natural killer cells (NK) and γδ T cells. This article will discuss the evolution of this method in clinical practice and the clinical outcome as described in different clinical trials.

Haploidentical Hematopoietic Stem Cell Transplantation as a Platform for Post-Transplantation Cellular Therapy

Haploidentical transplantation can extend the opportunity for transplantation to almost all patients who lack an HLA-matched donor. Advances in the field of haploidentical transplantation have led to a marked decrease in treatment-related mortality, allowing investigators to focus on developing rationale pre- and peri-remission therapies aimed at preventing disease relapse after transplantation. Because of widespread availability, low treatment-related mortality, and cost, haploidentical donors may become the preferred "alternative" donors for allogeneic hematopoietic stem cell transplantation. One of the major advantages of using a related donor is the possibility of collecting or generating additional cellular products from the same immediately available donor, which will not be rejected. Infusion of these cells in the peri-transplantation period, derived from the same immune system, is opening the possibility of markedly enhancing the antitumor effects of the graft and hastening immunologic reconstitution after transplantation.

Improved engraftment with minimal graft-versus-host disease after major histocompatibility complex-mismatched cord blood transplantation with photochemically treated donor lymphocytes

There is a significant risk of severe graft-versus-host disease (GVHD) and graft failure after unrelated umbilical cord blood transplantation (CBT) if donor-recipient pairs are mismatched at major histocompatibility complex (MHC) loci. To mitigate these risks after MHC-mismatched CBT, we infused psoralen-treated, photochemically inactivated, mature donor T-lymphocytes with MHC (H2-haplotype) mismatched murine donor fetal near-term peripheral blood (FNPB) cells after sublethal irradiation. We analyzed the rates of donor engraftment, GVHD and long-term survival in H2 haplotype disparate (C57BL/6 [H-2(b)/Thy1.1] → AKR [H-2(k)/Thy1.2]) recipient mice. We observed inconsistent donor engraftment after transplantation with cord blood alone, but superior engraftment and long-term survival after FNPB transplantation supplemented with psoralen-treated donor T-lymphocytes. Additionally, there was fatal GVHD after FNPB co-infusion with untreated donor T-lymphocytes, but minimal GVHD after FNPB supplemented with psoralen-treated donor T-lymphocytes transplantation. Donor MHC(high)/c-Kit(+)/lineage(-)/CD34(-) stem cells were noted in the recipient bone marrow compartment following co-infusion of photochemically inactivated T-cells with FNPB. Despite the non-myeloablative preparation before FNPB infusion, complete hematological recovery was delayed until 50-60 d after transplantation. We observed that co-transplantation of psoralen-treated donor T-lymphocytes with FNPB facilitated durable engraftment of donor hematopoietic stem cells in the marrow and splenic compartments with complete but delayed recovery of all hematopoietic lineages. This CBT model establishes the possibility of ensuring donor engraftment across a MHC barrier without severe GVHD.

Gammadelta T-cells: potential regulators of the post-burn inflammatory response

Severe burn induces an immunopathological response that contributes to the development of a systemic inflammatory response (SIRS) and subsequent multiple organ failure. While, multiple immune cells type (T-cells, macrophages, neutrophils) are involved in this response, recent evidence suggests that a unique T-cell subset, gammadelta T-cells are central in the response to injury. While gammadelta T-cells represent only a small percentage of the total T-cell population, they display specific functional characteristics that uniquely position them in the immune/inflammatory axis to influence a number of important aspects of the body's response to burn. This review will focus on the potential regulator role of gammadelta T-cells in immunopathological response following burn and thereby their potential as therapeutic targets for affecting inflammation and healing.

Immunobiology of allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (HSCT) has evolved into an effective adoptive cellular immunotherapy for the treatment of a number of cancers. The immunobiology of allogeneic HSCT is unique in transplantation in that it involves potential immune recognition and attack between both donor and host. Much of the immunobiology of allogeneic HSCT has been gleaned from preclinical models and correlation with clinical observations. We review our current understanding of some of the issues that affect the success of this therapy, including host-versus-graft (HVG) reactions, graft-versus-host disease (GVHD), graft-versus-tumor (GVT) activity, and restoration of functional immunity to prevent transplant-related opportunistic infections. We also review new strategies to optimize the GVT and improve overall immune function while reducing GVHD and graft rejection.

Gammadelta T cells do not require fully functional cytotoxic pathways or the ability to recognize recipient alloantigens to prevent graft rejection

Gammadelta T cells are a unique and minor T-cell subset that differs from conventional alphabeta T cells by virtue of their tissue localization and antigen processing requirements. We have previously shown that ex vivo-activated gammadelta T cells are able to prevent graft rejection without causing clinically significant graft-versus-host disease (GVHD). In the present study, we examined how gammadelta T cells facilitate alloengraftment and to what extent mechanisms used by conventional alphabeta T cells are also used by gammadelta T cells. We observed that, unlike alphabeta T cells, for which CD8(+) T cells are primarily responsible for facilitating engraftment, purified CD8(+)gammadelta(+) T cells administered at the same fractional dose as for the unseparated activated gammadelta T-cell population were insufficient to prevent graft rejection. Furthermore, the ability to prevent graft rejection was not affected by the absence of fully functional fas ligand or perforin cytotoxic pathways, nor was it contingent on the ability of gammadelta T cells to recognize recipient major histocompatibility process alloantigens. Repetitive infusions of a suboptimal dose of gammadelta T cells however were able to rescue mice from graft rejection, suggesting that the persistence of these cells in vivo was critical in facilitating alloengraftment. These studies demonstrate that gammadelta T cells do not use mechanisms used by conventional nontolerant alphabeta T cells to prevent graft rejection. The ability of these cells to promote engraftment without causing GVHD further distinguishes these cells from alphabeta T cells and may be an attribute that can be exploited in the clinical transplantation setting.

The tale of early hematopoietic cell seeding in the bone marrow niche

Since introduction of the notion of a "niche" that hosts engraftment and activity of hematopoietic cells, there is a massive effort to discover its structure and decipher its function. Our understanding of the niche is continuously changing with reinterpretation of traditional concepts and apprehension of new insights into the biology of hematopoietic cell homing, seeding, and engraftment. Here we discuss some of the early events in hematopoietic stem cell seeding and engraftment and propose a perspective based on visualization of labeled bone marrow cells in real time in vivo. Primary seeding of hematopoietic cells in the bone marrow niches evolves as a complex and dynamic process; however, it follows discrete topological and chronological patterns. Initial seeding occurs on the endosteal surface of the marrow, which includes heterogeneous niches for primary seeding. Several days after transplantation the endosteal niches become more restrictive, hosting primarily mitotically quiescent cells, and gradual centripetal migration is accompanied by engagement in proliferation and differentiation. The hematopoietic niches evolve as heterogeneous three-dimensional microenvironments that are continuously changing over time.

gammadelta T cells: a new frontier for immunotherapy?

The use of cytolytic effector cells as therapy for malignant disease has been a central focus of basic and clinical research for nearly 2 decades. Since the original descriptions of in vitro lymphocyte-mediated cytotoxicity against human tumor cells, there have been numerous attempts to exploit such observations for therapeutic use, with decidedly mixed results. Most studies have focused on the role of either natural killer cells or cytotoxic CD8 + alphabeta T cells as the primary mediators of antitumor cytotoxicity, and until recently little attention has been paid to the role of gammadelta T cells in this capacity. This is partially due to a lack of understanding of the mechanisms of gammadelta T-cell immune responses to tumors, as well as the practical problem of obtaining a sufficient number of gammadelta T cells for clinical-scale administration. In this article, we discuss the biological and clinical rationale for developing gammadelta T cell-based immunotherapies for the treatment of a variety of malignant conditions. It is our view that infusing supraphysiological numbers of tumor-reactive gammadelta T cells-either in the autologous or allogeneic setting-might be used to restore or augment innate immune responses against malignancies. Accordingly, we will also discuss how we and others are working to overcome some of the practical limitations that have so far limited the direct clinical delivery of highly purified human gammadelta T cells for the treatment of both hematologic and solid tumors.

Critical role of host gammadelta T cells in experimental acute graft-versus-host disease

Gammadelta T cells localize to target tissues of graft-versus-host disease (GVHD) and therefore we investigated the role of host gammadelta T cells in the pathogenesis of acute GVHD in several well-characterized allogeneic bone marrow transplantation (BMT) models. Depletion of host gammadelta T cells in wild-type (wt) B6 recipients by administration of anti-T-cell receptor (TCR) gammadelta monoclonal antibody reduced GVHD, and gammadelta T-cell-deficient (gammadelta-/-) BM transplant recipients experienced markedly improved survival compared with normal controls (63% vs 10%, P < .001). gammadelta T cells were responsible for this difference because reconstitution of gammadelta-/- recipients with gammadelta T cells restored GVHD mortality. gammadelta-/- recipients showed decreased serum levels of tumor necrosis factor alpha (TNF-alpha), less GVHD histopathologic damage, and reduced donor T-cell expansion. Mechanistic analysis of this phenomenon demonstrated that dendritic cells (DCs) from gammadelta-/- recipients exhibited less allostimulatory capacity compared to wt DCs after irradiation. Normal DCs derived from BM caused greater allogeneic T-cell proliferation when cocultured with gammadelta T cells than DCs cocultured with medium alone. This enhancement did not depend on interferon gamma (IFN-gamma), TNF-alpha, or CD40 ligand but did depend on cell-to-cell contact. These data demonstrated that the host gammadelta T cells exacerbate GVHD by enhancing the allostimulatory capacity of host antigen-presenting cells.

Graft facilitating cells are derived from hematopoietic stem cells and functionally require CD3, but are distinct from T lymphocytes

OBJECTIVE

We previously demonstrated that CD8(+)/TCR(-) bone marrow cells facilitate engraftment of HSC in allogeneic recipients without causing graft-vs-host disease. Whether facilitating cells (FC) develop from T cells or represent a distinct lineage has not been determined.

METHODS

In the present studies, we characterized the lineage derivation of FC, defined the role for the CD3 complex in allogeneic facilitation, and demonstrated syngeneic facilitation by FC but not T cells.

RESULTS

We demonstrate for the first time that FC development and function is independent of T cells and cannot be replaced by them. Purified GFP(+) HSC transplanted in syngeneic recipients produce GFP(+) FC, which facilitate in secondary transplants, confirming that FC are derived from HSC. In addition, FC, but not T cells, potently facilitate the engraftment of suboptimal numbers of HSC in syngeneic recipients. Notably, FC contain the transcripts for CD3 epsilon and CD3 delta, but not TCR alpha or TCR beta, excluding the possibility of T-cell contamination. Genetic mutations that generate a functional deficiency in CD3 signaling significantly impair FC function in allogeneic facilitation (p=0.006).

CONCLUSION

Taken together, these data clearly distinguish FC from T cells. Moreover, they indicate that FC require the CD3 epsilon gene to facilitate allogeneic HSC engraftment. The unique function(s) of FC make them an attractive focus for new cell-based therapeutic approaches to enhance HSC engraftment while reducing toxicity, especially when limiting numbers of HSC are available.

Transplanted hematopoietic cells seed in clusters in recipient bone marrow in vivo

The process of hematopoietic stem and progenitor cell (HSPC) seeding in recipient bone marrow (BM) early after transplantation is not fully characterized. In vivo tracking of HSPCs, labeled with PKH dyes, through an optical window surgically implanted on the mouse femur revealed that transplanted cells cluster in the recipient BM. Within the first day after intravenous injection, 86 +/- 6% of the cells seeded in clusters (p < 0.001 versus scattered cells) in the endosteal surfaces of the epiphyses. The primary clusters were formed by concomitant seeding of 6-10 cells over an area of approximately 70 microm, and secondarily injected cells did not join the already existing clusters but formed new clusters. Major antigen-disparate HSPCs participated in formation of the primary clusters, and T lymphocytes were also incorporated. After 4 to 5 days, some cellular clusters were observed in the more central regions of the BM, where the brightness of PKH fluorescence decreased, indicating cellular division. These later clusters were classified as secondary, assuming that the mechanisms of migration in the BM might be different from those of primary seeding. Some clusters remained in the periphery of the BM and retained bright fluorescence, indicating cellular quiescence. The number of brightly fluorescent cells in the clusters decreased exponentially to two to three cells after 24 days (p < 0.001). The data suggest that the hematopoietic niche is a functional unit of the BM stromal microenvironment that hosts seeding of a number of transplanted cells, which form a cluster. This may be the site where auxiliary non-HSPC cells, such as T lymphocytes, act in support of HSPC engraftment.

Non-myeloablative transplants for congenital diseases

The morbidity and mortality associated with postnatal HSCT, toxicity of HSCT conditioning regimens, lifelong immunosuppressive therapy, and lack of compatible donors discourages many patients and physicians from utilizing postnatal HSCT as a treatment for congenital disease. Non-myeloblative in utero HSCT is now being considered as an alternate treatment with the hope that it will be more therapeutic with less toxicity to a wider spectrum of patients with congenital disorders. Prenatal stem cell transfer may eliminate many of the risks and hazards associated with postnatal HSCT, as the fetus may be less reactive than an immunologically mature individual such that tolerance to donor cells could be developed. GVHD and rejection of postnatal therapeutic grafts may be minimized thus reducing or eliminating altogether the need for postnatal myeloablation and immunosuppression. Much work must be done both in animal studies as well as in clinical trials. By using well-designed murine models such as the beta-thalassemic mouse outlined above, we believe we can determine the optimal conditions for non-myeloablative postnatal transplants with allogeneic or haplocompatible HSC following prenatal tolerance induction with these cells. In addition, we may answer basic immunology questions regarding the development and regulation of immunity and tolerance in both mice and humans.

The role of alphabeta- and gammadelta-T cells in allogenic donor marrow on engraftment, chimerism, and graft-versus-host disease

BACKGROUND

We previously characterized a facilitating cell (FC) in mouse marrow that enables engraftment of allogeneic hematopoietic stem cells (HSCs) without causing graft-versus-host disease (GVHD). The FC shares some cell surface molecules with T cells (Thy1+, CD3epsilon+, CD8+, CD5+, and CD2+) but is T-cell receptor (TCR) negative. Historically, depletion of CD3+ or CD8+ cells from rat marrow was associated with an increased rate of failure of engraftment. In this study, we evaluated whether depletion of alphabeta- and gammadelta-TCR(+) T cells from donor marrow would retain engraftment potential yet avoid GVHD.

METHODS

Wistar-Furth rats were conditioned with 950 cGy of total body irradiation and transplanted with ACI bone marrow processed to remove either alphabeta-TCR(+), gammadelta-TCR(+), or alphabeta- plus gammadelta-TCR(+) T cells. Recipients were typed for chimerism at 28 days and monthly thereafter.

RESULTS

Recipients of marrow depleted of alphabeta- (group A), gammadelta- (group B), or alphabeta- and gammadelta-TCR(+) T cells (group C) engrafted and had an average chimerism level of 73.0+/-8.3%, 92.3+/-9.2%, and 46.3+/-32.8%, respectively. Aggressive T-cell depletion did not remove the FC population (CD8+/CD3+/TCR(-)). Group A and group B both developed GVHD, with a higher incidence of GVHD in group B compared to group A. None of the recipients in group C developed GVHD.

CONCLUSIONS

These data demonstrate that depletion of T cells from rat marrow does not impair engraftment of HSCs, indirectly supporting the existence of FCs in rat marrow. Moreover, donor alphabeta- and gammadelta-TCR(+) T cells contribute to GVHD in a nonredundant fashion, although alphabeta-TCR(+) T cells are more potent as the effector cells. Finally, the level of donor chimerism is influenced by the composition of the graft, because recipients of marrow that contain alphabeta-TCR(+) T cells exhibited significantly higher donor chimerism compared to recipients of marrow depleted of both alphabeta- and gammadelta-TCR(+) T cells.

Rantes production during development of cardiac allograft vasculopathy

BACKGROUND

RANTES (regulated on activation, normal T cell expressed and secreted) production has been shown to correlate with mononuclear cell recruitment and precede intimal thickening in cardiac allograft vasculopathy (CAV). However, the cells that produce RANTES in CAV are undefined. Therefore, in an MHC II-mismatched murine model of CAV, we sought to (1) define the cellular sources of RANTES and (2) determine the role of CD4+ lymphocytes in RANTES production during CAV development.

METHODS

B6.CH-2bm12 strain donor hearts were transplanted heterotopically into wild-type (WT) or CD4 knockout (CD4KO) C57BL/6 mice (MHC II mismatch). No immunosuppression was used. Recipients were sacrificed at 7, 14, and 24 days. Intragraft RANTES gene expression and protein levels were determined with ribonuclease protection assay and ELISA, respectively. At days 7 and 24, RANTES production by graft-infiltrating cells was defined with intracellular RANTES staining and multicolor FACS analysis. Intimal thickening was quantitated morphometrically. In murine hearts and in six explanted human hearts with advanced CAV, RANTES was also localized immunohistochemically.

RESULTS

NK, NKT, and gammadelta+ cells, in addition to CD4+, CD8+ lymphocytes, and CD11b+ macrophages, produced RANTES in early and late stages of CAV. RANTES-producing NK, NKT, and gammadelta+ cells tripled in number during CAV development; by day 24, NK and gammadelta+ cells each outnumbered CD4+ lymphocytes and CD11b+ macrophages. The presence of CD4+ lymphocytes was required for sustained RANTES production in allografts, which correlated with mononuclear cell recruitment and preceded intimal thickening. In murine and explanted human hearts with advanced CAV, RANTES immunolocalized with graft-infiltrating mononuclear cells and vessel wall cells.

CONCLUSIONS

We present evidence that other cell types in addition to CD4+, CD8+ T lymphocytes, and CD11b+ macrophages contribute significantly to RANTES production in CAV. In this MHC II-mismatched murine model of CAV, sustained RANTES production requires CD4+ lymphocytes, correlates with mononuclear cell recruitment, and precedes intimal thickening. In experimental and human CAV, vessel wall cells may also produce RANTES. Interventions aimed at inhibiting RANTES production in CAV may need to target several types of cells, and neutralization of RANTES bioactivity may reduce mononuclear cell recruitment and CAV development.

Both gamma delta T cells and NK cells inhibit the engraftment of xenogeneic rat bone marrow cells and the induction of xenograft tolerance in mice

In murine allogeneic bone marrow transplantation recipients, treatment of the hosts with a nonmyeloablative regimen, including depleting anti-CD4 and anti-CD8 mAbs, allows establishment of long-term mixed chimerism and donor-specific tolerance. However, in the xenogeneic rat-to-mouse combination, additional anti-Thy1.2 and anti-NK1.1 mAbs are required. We have now attempted to identify the xenoresistant mouse cell populations that are targeted by anti-NK1.1 and anti-Thy1.2 mAbs. C57BL/6 (B6) wild-type, B6 TCRbeta(-/-), and B6 TCRdelta(-/-) mice received anti-CD4 and anti-CD8 mAbs, followed by 3 Gy of whole body irradiation, 7 Gy of thymic irradiation, and transplantation of T cell-depleted rat bone marrow cells. Anti-NK1.1 and anti-Thy1.2 mAbs were additionally administered to some groups. Increased rat chimerism was observed in TCRdelta(-/-) mice treated with anti-CD4, anti-CD8, and anti-NK1.1 mAbs compared with similarly treated TCRbeta(-/-) mice. In TCRbeta(-/-) mice, but not in TCR delta(-/-) mice, donor chimerism was increased by treatment with anti-Thy1.2 mAb, indicating that CD4(-)CD8(-)TCRgammadelta(+)Thy1. 2(+)NK1.1(-) cells (gammadelta T cells) are involved in the rejection of rat marrow. In addition, chimerism was enhanced in both TCRbeta(-/-) and TCRdelta(-/-) mice treated with anti-CD4, anti-CD8, and anti-Thy1.2 mAbs by the addition of anti-NK1.1 mAb to the conditioning regimen. Donor-specific skin graft prolongation was enhanced by anti-Thy1.2 and anti-NK1.1 mAbs in TCRdelta(-/-) mice. Therefore, in addition to CD4 and CD8 T cells, gammadelta T cells and NK cells play a role in resisting engraftment of rat marrow and the induction of xenograft tolerance in mice.

CD2-mediated IL-12–dependent signals render human γδ-T cells resistant to mitogen-induced apoptosis, permitting the large-scale ex vivo expansion of functionally distinct lymphocytes: implications for the development of adoptive immunotherapy strategies

The ability of human γδ-T cells to mediate a number of in vitro functions, including innate antitumor and antiviral activity, suggests these cells can be exploited in selected examples of adoptive immunotherapy. To date, however, studies to examine such issues on a clinical scale have not been possible, owing in large measure to the difficulty of obtaining sufficient numbers of viable human γδ-T cells given their relative infrequency in readily available tissues. Standard methods used to expand human T cells often use a combination of mitogens, such as anti–T-cell receptor antibody OKT3 and interleukin (IL)-2. These stimuli, though promoting the expansion of αβ-T cells, usually do not promote the efficient expansion of γδ-T cells. CD2-mediated, IL-12–dependent signals that result in the selective expansion of human γδ-T cells from cultures of mitogen-stimulated human peripheral blood mononuclear cells are identified. It is first established that human γδ-T cells are exquisitely sensitive to apoptosis induced by T-cell mitogens OKT3 and IL-2. Next it is shown that the CD2-mediated IL-12–dependent signals, which lead to the expansion of γδ-T cells, do so by selectively protecting subsets of human γδ-T cells from mitogen-induced apoptosis. Finally, it is demonstrated that apoptosis-resistant γδ-T cells are capable of mediating significant antitumor cytotoxicity against a panel of human-derived tumor cell lines in vitro. Both the biologic and the practical implications of induced resistance to apoptosis in γδ-T cells are considered and discussed because these findings may play a role in the development of new forms of adoptive cellular immunotherapy.

CD2-mediated IL-12–dependent signals render human γδ-T cells resistant to mitogen-induced apoptosis, permitting the large-scale ex vivo expansion of functionally distinct lymphocytes: implications for the development of adoptive immunotherapy strategies

The ability of human γδ-T cells to mediate a number of in vitro functions, including innate antitumor and antiviral activity, suggests these cells can be exploited in selected examples of adoptive immunotherapy. To date, however, studies to examine such issues on a clinical scale have not been possible, owing in large measure to the difficulty of obtaining sufficient numbers of viable human γδ-T cells given their relative infrequency in readily available tissues. Standard methods used to expand human T cells often use a combination of mitogens, such as anti–T-cell receptor antibody OKT3 and interleukin (IL)-2. These stimuli, though promoting the expansion of αβ-T cells, usually do not promote the efficient expansion of γδ-T cells. CD2-mediated, IL-12–dependent signals that result in the selective expansion of human γδ-T cells from cultures of mitogen-stimulated human peripheral blood mononuclear cells are identified. It is first established that human γδ-T cells are exquisitely sensitive to apoptosis induced by T-cell mitogens OKT3 and IL-2. Next it is shown that the CD2-mediated IL-12–dependent signals, which lead to the expansion of γδ-T cells, do so by selectively protecting subsets of human γδ-T cells from mitogen-induced apoptosis. Finally, it is demonstrated that apoptosis-resistant γδ-T cells are capable of mediating significant antitumor cytotoxicity against a panel of human-derived tumor cell lines in vitro. Both the biologic and the practical implications of induced resistance to apoptosis in γδ-T cells are considered and discussed because these findings may play a role in the development of new forms of adoptive cellular immunotherapy.

Adoptively transferred gamma delta T cells indirectly regulate murine graft-versus-host reactivity following donor leukocyte infusion therapy in mice

The purpose of this study was to determine whether gamma delta T cells were able to regulate graft-vs-host (GVH) reactivity mediated by alpha beta T cells in murine recipients transplanted with MHC-mismatched marrow grafts. Studies were conducted using ex vivo-activated gamma delta T cells because this was a more clinically relevant strategy, and these cells have been shown to be capable of facilitating alloengraftment without causing GVH disease (GVHD). Coadministration of activated gamma delta T cells and naive alpha beta T cells at the time of bone marrow transplantation (BMT) significantly exacerbated GVHD when compared with naive alpha beta T cells alone. In contrast, when the administration of naive alpha beta T cells was delayed for 2 wk post-BMT, survival was significantly enhanced in mice transplanted with BM plus activated gamma delta T cells vs those given marrow cells alone. Mitigation of GVHD by activated gamma delta T cells occurred only at high doses (150 x 106) and was a unique property of gamma delta T cells, as activated alpha beta T cells were incapable of ameliorating the subsequent development of GVHD. Protection from GVHD was not due to the direct inhibition of naive alpha beta T cells by gamma delta T cells. Rather, gamma delta T cells mediated this effect indirectly through donor BM-derived alpha beta T cells that acted as the proximate regulatory population responsible for the decrease in GVH reactivity. Collectively, these data demonstrate that activated gamma delta T cells are capable of modulating the ability of MHC-incompatible nontolerant alpha beta T cells to cause GVHD after allogeneic BMT.

CD8+TCR+ and CD8+TCR- cells in whole bone marrow facilitate the engraftment of hematopoietic stem cells across allogeneic barriers

Although purified hematopoietic stem cells (HSC) are sufficient to engraft irradiated allogeneic recipients, bone marrow (BM) contains other cells that facilitate engraftment. Here, several candidate facilitators were tested by cotransplantation with HSC. Both TCR+ and TCR- CD8alpha+ BM subpopulations have facilitative potential. CD8+TCR+ cells are typical T lymphocytes. CD8+TCR- facilitators are CD3 , not CD3+, have a granular morphology, and are CD8beta- and CD11c+; they share phenotypic characteristics with CD8(alpha)alpha lymphoid dendritic cells and veto cells. We also demonstrate that lytic function is nqt necessary for facilitation and that the CD8alpha molecule is either important for facilitation or in the development of facilitators.

Allogeneic transplantation from donors other than HLA-identical siblings

The decade of the 1990s has witnessed impressive advances in the use of alternative donors for allogeneic transplantations. Through funded collaborative, and single-center research efforts, there is great promise that complete and equal access to allogeneic transplantation will be realized. In the next decade, universal donor availability should maximize the patient's chance of overcoming otherwise fatal disease.

Stable engraftment after megadose blood stem cell transplantation across the HLA barrier: the case for natural killer cells as graft-facilitating cells

BACKGROUND

The case of a patient with chronic myelogenous leukemia who underwent transplantation with highly purified CD34+ peripheral blood stem cells from his two-antigen-mismatched mother is reported. No graft-versus-host disease has been observed so far and stable engraftment has been documented until day 100.

METHODS

Weekly analysis of chimerism in different cellular subsets was performed using a quantitative polymerase chain reaction assay for nine short tandem repeat markers in leukocytes sorted by fluorescence-activated cell sorting.

RESULTS

No donor CD4+ or CD8+ T cells have been detected up to 3 months after transplantation, whereas a rapid increase of donor CD56+ natural killer (NK) cells was observed in parallel with circulating donor CD34+ progenitors and myeloid cells.

CONCLUSIONS

Because the graft contained virtually no T and NK cells, we believe the rapid in vivo generation of NK cells supported stable engraftment across the HLA barrier. The differentiation of CD34+ progenitors into NK cells might be a distinct feature of megadose stem cell transplants.

The use of an anti-TCRalphabeta monoclonal antibody to control host-versus-graft reactions in canine marrow allograft recipients conditioned with low dose total body irradiation

BACKGROUND

A limitation in the application of marrow transplantation has been complications related to the conditioning regimens that have been intensified to the point where organ toxicities have been common, resulting in morbidity and mortality.

METHODS

A conditioning regimen consisting of low-dose total body irradiation (TBI*) was used to test whether postgrafting therapy with a monoclonal antibody (mAb) against the T cell receptor (TCR)alphabeta facilitated sustained engraftment of marrow from dog leukocyte antigen (DLA)-identical canine littermates. The anti-TCRalphabeta mAb 15.9D5 was selected for in vivo studies because it induced hyporesponsiveness to allogeneic stimulator cells in mixed leukocyte culture and was not mitogenic in vitro.

RESULTS

When recipients of genotypically DLA-identical marrow were conditioned by the barely "lethal" dose of 450 cGy TBI alone, almost 60% of grafts failed (n=39). The remainder engrafted, either in the form of stable mixed donor/host or all donor hematopoietic chimerism. In contrast to results in controls, 5 of 6 dogs that were given, in addition, a loading dose of mAb 15.9D5 of 1 mg/kg on day -1, 450 cGy TBI on day 0, followed by mAb at 0.3 mg/kg/day until day +7, showed sustained engraftment (P=.058). To accomplish a comparable rate of engraftment in the absence of anti-TCRalphabeta antibody, 920 cGy TBI were needed for pretransplant conditioning.

CONCLUSIONS

Results strongly suggested that in vivo administration of a mAb against TCRalphabeta prevented rejection of allogeneic marrow grafts in the setting of conditioning with a relatively nontoxic but otherwise suboptimal dose of 450 cGy TBI. In vivo administration of m Ab 15.9D5 was well tolerated without any noticeable side effects. The exact mechanism by which the mAb works in vivo is as yet poorly understood, but it does not involve CD3/TCR complex modulation or elimination of T cells from the circulation.

Ex Vivo Anti-CD3 Antibody-Activated Donor T Cells Have a Reduced Ability to Cause Lethal Murine Graft-Versus-Host Disease but Retain Their Ability to Facilitate Alloengraftment

The purpose of this study was to determine whether ex vivo anti-CD3 Ab-activated T cells behaved in a biologically similar manner as naive T cells with respect to causing graft-vs-host disease (GVHD) and facilitating engraftment after allogeneic marrow transplantation. This question was addressed using two well-defined MHC-incompatible murine models of GVHD (C57BL/6 (H-2b)→B10.BR (H-2k)) and engraftment (C57BL/6 (H-2b)→AKR/J (H-2k)). Transplantation with anti-CD3-activated T cells significantly reduced GVHD compared with that in animals transplanted with equivalent numbers of naive T cells. Protection from GVHD was not T cell subset dependent, as highly enriched populations of either activated CD4+ or CD8+ T cells caused less lethal GVHD than comparable numbers of purified naive CD4+ or CD8+ T cells. Transplantation with activated T cells also resulted in protection from LPS-mediated GVH lethality in unirradiated F1 recipients. Analysis of immune recovery indicated that animals transplanted with activated T cells had thymic and splenic B cell reconstitution that compared favorably to that in non-GVHD control mice. When engraftment was analyzed, equivalent degrees of donor cell engraftment were observed when animals were transplanted with limiting numbers (5 × 105) of naive vs activated B6 T cells. Further studies indicated that activated CD8+ T cells were exclusively responsible for enhancing engraftment and that facilitation of engraftment was dependent upon the direct recognition of host MHC alloantigens. Collectively, these data demonstrate that transplantation with anti-CD3 Ab-activated T cells results in a reduction in GVHD, but these cells retain their ability to facilitate alloengraftment. The use of this approach in allogeneic marrow transplantation may represent an alternative strategy to mitigate GVHD without compromising engraftment.

Prevention of Marrow Graft Rejection Without Induction of Graft-Versus-Host Disease by a Cytotoxic T-Cell Clone That Recognizes Recipient Alloantigens

In allogeneic marrow transplantation, donor T cells that recognize recipient alloantigens prevent rejection but also cause graft-versus-host disease (GVHD). To evaluate whether the ability to prevent marrow graft rejection could be dissociated from the ability to cause GVHD, we generated a panel of four different CD8 cytotoxic T-lymphocyte clones specific for H2d alloantigens. Three of the clones caused no overt toxicity when as many as 20 × 106 cells were infused intravenously into irradiated H2d-positive recipients, and one clone caused acute lethal toxicity within 1 to 3 days after transferring 10 × 106cells into H2d-positive recipients. One clone that did not cause toxicity was able to prevent rejection of (C57BL/6J × C3H/HeJ)F1 marrow in 800 cGy-irradiated (BALB/cJ × C57BL/6J)F1 recipients without causing GVHD. Large numbers of cells and exogenously administered interleukin-2 were required to prevent rejection. These results with different CD8 clones suggest that GVHD and prevention of rejection could be separable effects mediated by distinct populations of donor T cells that recognize recipient alloantigens.

Prevention of Marrow Graft Rejection Without Induction of Graft-Versus-Host Disease by a Cytotoxic T-Cell Clone That Recognizes Recipient Alloantigens

In allogeneic marrow transplantation, donor T cells that recognize recipient alloantigens prevent rejection but also cause graft-versus-host disease (GVHD). To evaluate whether the ability to prevent marrow graft rejection could be dissociated from the ability to cause GVHD, we generated a panel of four different CD8 cytotoxic T-lymphocyte clones specific for H2d alloantigens. Three of the clones caused no overt toxicity when as many as 20 × 106 cells were infused intravenously into irradiated H2d-positive recipients, and one clone caused acute lethal toxicity within 1 to 3 days after transferring 10 × 106cells into H2d-positive recipients. One clone that did not cause toxicity was able to prevent rejection of (C57BL/6J × C3H/HeJ)F1 marrow in 800 cGy-irradiated (BALB/cJ × C57BL/6J)F1 recipients without causing GVHD. Large numbers of cells and exogenously administered interleukin-2 were required to prevent rejection. These results with different CD8 clones suggest that GVHD and prevention of rejection could be separable effects mediated by distinct populations of donor T cells that recognize recipient alloantigens.