Kimberly L. Gandy

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.

From stem cells to lymphocytes; biology and transplantation

Summary: We review the development of the hematopoietic system, focusing on the transition from hematopoietic stem cells (HSCs) to T cell This includes the isolation of HSCs, and recent progress in understanding their ontogeny, homing properties, and differentiation. HSC transplantation is reviewed, including the kinetics of reconstitution, engraftment across histocompatibility barriers, the facilitation of allogeneic engraftment, and the mechanisms of graft rejection. We describe progress in understanding T‐cell development in the bone marrow and thymus as well as the establishment of lymph nodes. Finally, the role of bcl‐2 in regulating homeostasis in the hematopoietic system is discussed.

Tolerance of allogeneic heart grafts in mice simultaneously reconstituted with purified allogeneic hematopoietic stem cells.

BACKGROUND Animals reconstituted with allogeneic whole bone marrow (WBM) are often tolerant of donor-specific solid organ grafts. Clinical application of bone marrow transplantation in solid organ transplantation has been limited, however, principally by graft-versus-host disease. We previously demonstrated that hematopoietic stem cells (HSCs) reconstitute lethally irradiated allogeneic mice without producing graft-versus-host disease. The purpose of this study was to determine whether tolerance to solid organ grafts could be induced in mice reconstituted with HSCs. METHODS BALB/c mice were lethally irradiated and reconstituted with allogeneic C57BL/Ka, Thy-1.1 WBM or HSCs. An isolated group was given a limited number of HSCs (250 cells) and a subpopulation of allogeneic cells known to facilitate HSC engraftment (facilitators). C57BL/Ka, Thy-1.1 neonatal heart grafts were placed in reconstituted animals either at the time of hematopoietic transplant or 35 days later. Third-party C3H grafts were placed over 2 months after hematopoietic reconstitution. Tolerance was defined as the persistence of cardiac contraction for the duration of evaluation (125-270 days). RESULTS All surviving mice that were reconstituted with C57BL/Ka, Thy-1.1 HSCs, WBM, or HSCs and facilitators were tolerant of C57BL/Ka grafts long-term. Third-party C3H grafts placed in reconstituted animals were rejected by day 12, whereas those placed in unmanipulated mice were rejected by day 9. CONCLUSION These data indicate that tolerance to concurrently or subsequently placed solid organ grafts can be reliably achieved with limited numbers of purified HSCs in a model where immunocompetence to third-party major histocompatibility complex antigens is delayed but intact.

Role of mesenchymal stem cell therapy in Crohn's disease

Many trials of mesenchymal stem cells (MSCs) have been published in the past 5–6 y. MSCs inhibit T-cell alloreactivity in vitro by soluble factors and direct cell-to-cell contact. They are safe to infuse in humans with no acute toxicity and no ectopic tissue formation. Promising results of MSC infusion for graft-vs.-host disease and fistulizing Crohn’s disease (CD) have been published. Treatment of CD requires a comprehensive treatment approach to maintain symptomatic control, improve health-related quality-of-life measures, and minimize complications from the disease. In this review, we will discuss the results of clinical trials using a novel treatment in the form of MSCs for treatment of CD and related complications. Success of these phase I, II, and III trials have set the stage for usage of this novel treatment for children with CD.

Emerging uses for pediatric hematopoietic stem cells

Many new therapies are emerging that use hematopoietic stem and progenitor cells. In this review, we focus on five promising emerging trends that are altering stem cell usage in pediatrics: (i) The use of hematopoietic stem cell (HSC) transplantation, autologous or allogeneic, in the treatment of autoimmune disorders is one. (ii) The use of cord blood transplantation in patients with inherited metabolic disorders such as Hurler syndrome shows great benefit, even more so than replacement enzyme therapy. (iii) Experience with the delivery of gene therapy through stem cells is increasing, redefining the potential and limitations of this therapy. (iv) It has recently been shown that human immunodeficiency virus (HIV) infection can be cured by the use of selected stem cells. (v) Finally, it has long been postulated that HSC-transplantation can be used to induce tolerance in solid-organ transplant recipients. A new approach to tolerance induction using myeloid progenitor cells will be described.

Perinatal induction of immunotolerance to cardiac and pulmonary allografts

OBJECTIVES Tolerance appears to be more easily induced in the fetus before full immunocompetence is established, but elucidation of this process is needed. A model of perinatal tolerance induction to neonatal skin allografts followed by cardiac and pulmonary allografts is described. METHODS Sixty Lewis (RT11) rat fetuses were inoculated intraperitoneally at 18 days gestation with 1 x 10(7) ACI (RT1a) rat fetal liver cells (group I); 20 Lewis fetuses were inoculated with 2 x 10(7) ACI fetal liver cells (Group II). control groups consisted of Lewis fetuses inoculated with saline solution (n = 25, group III) and fetuses that were not inoculated (n = 25, group IV). Twenty-five of the 50 surviving group I rats received ACI skin (< 24 hours old) and heart (8 to 10 weeks old) allografts (group IA); the remaining 25 rats received only ACI heart grafts (group IB). Groups II, III, and IV received ACI skin and cardiac allografts. Recipients tolerant to both skin and cardiac grafts received orthotopic ACI lung grafts and third-party skin grafts. Tolerance was indicated by graft survival for more than 100 days. Limiting dilution and flow cytometric analyses were performed. RESULTS Abortion rates in groups I, II, III, and IV were 17% (10/60), 65% (13/20), 8% (2/25), and 4% (1/25), respectively. Specific tolerance to skin, cardiac, and lung allografts was observed in seven of 25 group IA recipients (28%) and seven of seven group II recipients (100%) compared with no tolerance in any group IB, III, or IV recipients (p = 0.03, chi 2 test). A 100-fold reduction of precursor cytotoxic T lymphocytes and significant splenocyte and bone marrow chimerism in tolerant versus nontolerant rats were noted (p = 0.0001, Students t test). CONCLUSIONS Using donor-strain fetal liver cells and neonatal skin grafts, we achieved higher frequencies of tolerance to solid organ grafts in adulthood with lower cell inocula and abortion rates than previously described. Chimerism and depressed precursor cytotoxic T lymphocyte frequencies in tolerant recipients suggest that hematopoietic stem cell engraftment and clonal deletion/anergy are involved in induction of perinatal tolerance.