Cord blood nucleated cells induce delayed T cell alloreactivity

Functional Heterogeneity of Umbilical Cord Blood Monocyte-Derived Dendritic Cells

Human umbilical cord blood (UCB) represents a unique resource for hematopoietic stem cell transplantation for children and patients lacking suitable donors. UCB harbors a diverse set of leukocytes such as professional APCs, including monocytes, that could act as a novel source for cellular therapies. However, the immunological properties of UCB monocytes and monocyte-derived dendritic cells (MoDCs) are not fully characterized. In this study, we characterized the phenotype and functions of UCB-MoDCs to gauge their potential for future applications. UCB exhibited higher frequencies of platelets and lymphocytes as well as lower frequencies of neutrophils in comparison with adult whole blood. Leukocyte subset evaluation revealed significantly lower frequencies of granulocytes, NK cells, and CD14+CD16- monocytes. Surface marker evaluation revealed significantly lower rates of costimulatory molecules CD80 and CD83 while chemokine receptors CCR7 and CXCR4, as well as markers for Ag presentation, were similarly expressed. UCB-MoDCs were sensitive to TLR1-9 stimulation and presented quantitative differences in the release of proinflammatory cytokines. UCB-MoDCs presented functional CCR7-, CXCR4-, and CCR5-associated migratory behavior as well as adequate receptor- and micropinocytosis-mediated Ag uptake. When cocultured with allogeneic T lymphocytes, UCB-MoDCs induced weak CD4+ T lymphocyte proliferation, CD71 expression, and release of IFN-γ and IL-2. Taken together, UCB-MoDCs present potentially advantageous properties for future medical applications.

T Cell-Mediated Rejection of Human CD34+ Cells Is Prevented by Costimulatory Blockade in a Xenograft Model

A xenograft model of stem cell rejection was developed by co-transplantating human CD34⁺ and allogeneic CD3⁺ T cells into NOD-scid ɣ-chain^null mice. T cells caused graft failure when transplanted at any CD34/CD3 ratio between 1:50 and 1:.1. Kinetics experiments showed that 2 weeks after transplantation CD34⁺ cells engrafted the marrow and T cells expanded in the spleen. Then, at 4 weeks only memory T cells populated both sites and rejected CD34⁺ cells. Blockade of T cell costimulation was tested by injecting the mice with abatacept (CTLA4-IgG1) from day -1 to +27 (group A), from day -1 to +13 (group B), or from day +14 to +28 (group C). On day +56 groups B and C had rejected the graft, whereas in group A graft failure was completely prevented, although with lower stem cell engraftment than in controls (P = .03). Retransplantation of group A mice with same CD34⁺ cells obtained a complete reconstitution of human myeloid and B cell lineages and excluded latent alloreactivity. In this first xenograft model of stem cell rejection we showed that transplantation of HLA mismatched CD34⁺ cells may be facilitated by treatment with abatacept and late stem cell boost.

Immunity Enhancement in Immunocompromised Gastrointestinal Cancer Patients with Allogeneic Umbilical Cord Blood Mononuclear Cell Transfusion

Objectives. In order to enhance the immunity of cancer patients to prevent relapse or to prolong survival time, umbilical cord blood mononuclear cells (UCMCs) were transplanted to cancer patients. Patients and Methods. UCMCs were transfused to 63 immunocompromised gastrointestinal cancer patients with nonmyeloablative (NMA) conditioning regimen. Results. The clinical study showed that the number of both T and B cells increased much more rapidly after transfusion of UCMCs than that of the control group without transplantation (p < 0.01). Proinflammation cytokines IFNγ and TNFα in serum increased to or above the normal range in 80.9% of patients at 12 weeks after UCMC transfusion. However, they recovered to the normal range in 21.7% of patients at the same time point in the control group only. In addition, the clinical investigation also showed that the transfusion of UCMC increased stable disease (SD) and reduced progressive disease (PD) significantly (p < 0.01); however, it did not have significant effects on complete response (CR), partial response (PR), or mortality rates compared with the control group (p > 0.05). Conclusions. UCMCs have powerful repairing effects on damaged cells and tissues and may reconstruct the impaired immunity. Transfusion of UCMCs could reconstruct the immunity of cancer patients with immunosuppression.

Donor-Derived Regulatory T Cells Attenuate the Severity of Acute Graft-Versus-Host Disease after Cord Blood Transplantation

Allogeneic peripheral blood stem cell transplantation (allo-PBSCT) is a curative therapy for some types of hematological disorders. However, allo-PBSCT is commonly complicated with acute graft-versus-host disease (aGVHD), characterized by host tissues being attacked by the grafted donor lymphocytes due to disparities of human leukocyte antigen (HLA) between the donor and host. By contrast, cord blood transplantation (CBT) is typically associated with low-grade severity of aGVHD, but the underlying mechanisms remain unclear. Donor-derived CD4(+) alloreactive T cells (ATs) are of a specific lymphocyte subset, which can be activated by the recipient's HLA, and play a crucial role in the onset of aGVHD. In the present study, we aimed to explore the difference in the property of CD4(+) ATs between cord blood (CB) and adult peripheral blood (APB). We thus found that CB and APB CD4(+) ATs contained not only effector T cells (Teffs) that execute aGVHD, but also a distinct subset of FoxP3(+) regulatory T cells (Tregs) that may alleviate aGVHD. Importantly, CB CD4(+) ATs contained higher percentage of FoxP3(+) Tregs, compared to APB CD4(+) ATs (P < 0.001), while lower percentage of Teffs (Th1, Th2 and Th17 cells) was detected in CB CD4(+) ATs (P < 0.05, P < 0.001 and P < 0.05, respectively). Our findings suggest that FoxP3(+) Tregs in CB CD4(+) ATs may contribute to attenuating the severity of aGVHD observed after CBT.

Immune regulatory cells in umbilical cord blood and their potential roles in transplantation tolerance

Umbilical cord blood (UCB) is a source of primitive hematopoietic stem (HSC) and progenitor cells, that served as an alternative to bone marrow (BM) for effective transplantation therapy. Success of HSC transplantation (HSCT) is limited in part by graft-versus-host disease (GVHD), graft rejection and delayed immune reconstitution, which all relate to immunological complications. GVHD after UCB transplantation is lower compared to that of BM HSCT. This may relate to the tolerogenic nature of T cells, mononuclear cells (MNCs) and especially immune regulatory cells existing in UCB. UCB contains limiting numbers of HSC or CD34(+) cell dose for adult patients resulting in delayed engraftment after UCB transplantation (UCBT). This needs to be improved for optimal transplantation outcomes. Approaches have been undertaken to promote HSC engraftment, including co-infusion of multiple units of UCB cells. These new methods however added additional immunological complications. Herein, we describe current knowledge on features of UCB immune cells, including regulatory T cells (Tregs) and mesenchymal stem/stromal cells (MSCs) and their potential future usage to reduce GVHD.

Alloreactivity from human viral specific memory T-cells

The mechanisms by which alloreactive memory T-cells are generated in non-sensitized individuals have begun to be elucidated. It is generally accepted that a very high level of crossreactivity is an essential feature of the T-cell receptor. Indeed it has recently been shown that alloreactivity from viral specific memory T-cells is far more common than predicted, 45% of viral specific T-cell clones were found to be allo-HLA crossreactive. In this overview the evidence for crossreactive alloresponses from human viral specific memory T-cells is discussed with special emphasis on the unexpected high frequency of these crossreactive responses, the peptide and tissue specificity of the responses, and the mechanistic insights gleaned from the elucidation of the crystal structure of an allo-HLA crossreactive viral specific TCR. The possible implications for clinical solid organ and bone marrow transplantation and tolerance induction will be discussed.