The effect of T lymphocyte depletion on neonatal tolerance induction, graft-vs.-host disease and cellular chimerism

Microchimerism and tolerance after in utero bone marrow transplantation in mice

BACKGROUND

Donor-specific tolerance has been induced after both fetal and neonatal hematopoietic stem cell (HSC) transplantation in mice. However, the relationship between hematopoietic microchimerism and tolerance in these models has not been defined due to the insensitivity of donor cell detection methodology. To address this problem we developed a semiquantitative polymerase chain reaction (PCR)-based assay for detection of microchimerism after major histocompatibility (MHC) class I disparate HSC transplantation. This assay was used to examine the relationship between microchimerism and tolerance after fetal and neonatal transplantation of fully allogeneic bone marrow cells.

MATERIALS AND METHODS

C57BL/6 mice (H2-Kb) were used as adult bone marrow donors and Balb/c mice (H2-Kd) were used as fetal or newborn recipients. A dose of 10(10) BM cells/kg was injected intraperitoneally into recipient animals. Peripheral blood of animals which survived beyond 3 weeks of age was analyzed by PCR for the presence of donor MHC class I DNA. Tolerance was tested by placement of donor-specific skin grafts after determination of chimerism status.

RESULTS

Our assay was found to be specific for H2-Kb donor cells in an H2-Kd background with a sensitivity of <0.0001%. Of 49 animals injected in utero 19 (38%) had donor DNA present in peripheral blood at low levels (<0.1%) whereas only 1 of 18 neonatally injected animals had detectable donor cells (P < 0.01). Tolerance to donor-specific skin grafts was found in 6 of 9 animals which were chimeric after in utero HSC transplantation whereas none of the 18 neonatally injected animals including the chimeric animal were tolerant.

CONCLUSIONS

Our results indicate the following. (<CITEREF RID="JR975255RF1">1) Hematopoietic microchimerism can be detected by PCR in peripheral blood after in utero injection of fully allogeneic HSCs. (<CITEREF RID="JR975255RF2">2) Fetal injections yield a higher incidence of microchimerism than newborn injections. (<CITEREF RID="JR975255RF3">3) Tolerance can be induced across a fully allogeneic barrier by in utero HSC transplantation and this is associated with the presence of peripheral blood microchimerism.

Transplantation of fetal cells

Cellular transplantation is an attractive alternative to whole-organ transplantation when only a discrete function of the organ is deficient. Early fetal donor cells have an advantage because they engraft readily and do not cause graft-versus-host disease. Similarly, the fetus is an ideal recipient of allogeneic fetal cells as it is incapable of rejecting them early in gestation. This review presents the theoretical rationale, recent research advances, and clinical implications for adults with diabetes mellitus and Parkinson's disease; we also describe in utero transplantation of fetal hematopoietic stem cells and hepatocytes for the treatment of inherited hematologic and hepatic deficiencies, as well as the use of fetal islet cells and dopamine-producing cells to treat postnatal conditions.

Persistence of anti-donor allohelper T cells after neonatal induction of allotolerance in mice

BALB/c mice rendered tolerant to A/J alloantigens by neonatal injection of 10(8) (A/J X BALB/c)F1 spleen cells develop an autoimmune disease associated with a polyclonal activation of donor B cells. To study the mechanisms leading to donor B cell activation in tolerant mice, we prepared mixed lymphocyte cultures (MLC) between splenic T cells from neonatally injected mice and donor-type (A/J X BALB/c)F1 or third-party (C57BL/6 X BALB/c)F1 B cells. T cells from tolerized mice were unable to generate cytotoxic T lymphocytes, to proliferate or to secrete interleukin (IL)2 after stimulation with donor alloantigens in MLC. These T cell responses were present after MLC with third-party antigens, but were of lower intensity than those generated by control BALB/c T cells. In contrast, T cells from tolerized mice stimulated immunoglobulin production by donor-type (A/J X BALB/c)F1 B cells much more powerfully than T cells from control BALB/c mice. The stimulation of donor-type (A/J X BALB/c)F1 B cells was polyclonal, as attested by the levels of anti-hapten and anti-DNA antibodies in the MLC supernatants. IgM was the dominant isotype secreted in vitro, but IgG1 and IgG3 were also produced in significant amounts. Lysis experiments indicated that the T cells responsible for F1 B cell stimulation in MLC were CD4+ host T cells. These T helper cells were alloreactive since they did not stimulate syngeneic BALB/c B cells, and their effect on donor B cells was specifically blocked by anti-donor Ia monoclonal antibodies. Addition of anti-IL 4 monoclonal antibody to MLC between T cells from tolerant mice and (A/J X BALB/c)F1 B cells almost completely abolished the production of IgG1, but not that of IgM or IgG3. Taken together, these findings indicate that neonatal injection of alloantigens in BALB/c mice induces a state of dissociated tolerance, with unresponsiveness of anti-donor T cells secreting IL 2 on the one hand, and persistence of T cells responsible for B cell help and IL 4 secretion on the other hand.

Establishment of a novel method to induce tolerance in adult mice across fully allogeneic (entire H-2 plus multiminor histocompatibility) antigen barriers, using supralethal irradiation followed by injection of syngeneic bone marrow cells plus (donor X recipient) F1 spleen cells

A novel method was established which can regularly induce profound tolerance in mice across entire H-2 plus multiminor histocompatibility (H) antigen (fully allogeneic) barriers. When recipient AKR/J Sea (AKR; H-2k) or C3H/He Slc (C3H; H-2k) mice were irradiated with 900 rad followed 1 day later by injection of 1 X 10(7) T cell-depleted syngeneic bone marrow cells plus 5 X 10(7) viable, but not mitomycin C-treated, [C57BL/6 Slc(B6) X AKR (or C3H)] F1 spleen cells via intravenous (i.v.) route, a specific tolerant state was induced against B6 (H-2b) antigens. In the tolerant C3H mice, the EL-4 tumor, which originates from B6, was accepted in a tolerogen-specific manner. Moreover, B6 skin grafts were permanently accepted in most of the tolerized AKR and C3H mice. Immunological parameters, including cytotoxic T lymphocyte (CTL) activity and the mixed lymphocyte reaction (MLR), were almost completely suppressed in the tolerant mice. An assay for chimerism using a direct immunofluorescence method revealed that the tolerant AKR mice were chimeric for the first 5 weeks after tolerance induction but not definitely chimeric thereafter. In the tolerant AKR mice, strong suppressor cells were not detected. This method could be used in order to investigate mechanisms of tolerance to allogeneic antigens in future experiments.

On the feasibility of inducing tolerance in man: a study in the cynomolgus monkey

Our previous work on the in vitro generation of cytotoxic T lymphocytes from the blood of 15-22-week-old fetuses, and on the induction of immunological tolerane in both radiation chimeras and neonatal mice, using T lymphocyte-depleted allogeneic bone marrow cells, has led us to believe that it should be possible to establish red cell chimerism in human fetuses by the infusion of allogeneic adult bone marrow cells. The essential prerequisite appears to be the removal of immunocompetent T lymphocytes from the bone marrow transplant, for new T cells generated from donor stem cells become tolerant to the histocompatibility antigens of the host's thymus and cannot, therefore, cause graft-versus-host disease (GVHD). Such an approach could be used in the treatment of fetuses diagnosed at an early stage as suffering from life-threatening inherited blood disorders. The experiments described here were designed to test this hypothesis in a sub-human primate species, Macaca fascicularis. Twenty-two cynomolgus monkeys received infusions of haploidentical (paternal) bone marrow between days 51 and 95 of gestation. There was no evidence of chimerism in animals inoculated after day 75 from mating. Eight out of 14 fetuses inoculated before day 70 were late intra-uterine deaths, four were hydropic and in one, histological confirmation of GVHD was obtained, indicating that tolerance can be induced at this time, as GVHD can occur only if donor cells survive. The T cell-depletion technique used here did not appear to prevent GVHD.

Neonatal tolerance induction to Mlsa. II. T cells induce tolerance to Mlsa

We have investigated the ability of murine T cell lines to induce neonatal tolerance to Mlsa (minor lymphocyte stimulating). Mlsb mice were injected within 24 hr of birth with MHC (major histocompatibility complex) identical T cell lines generated by culturing responders from Mlsa strains with stimulators from Mlsb strains. Injected mice were tested at 6 to 8 weeks of age for responses in either primary mixed leukocyte reaction or IL-2 limiting dilution analysis. Mlsa specific responses by injected tolerant mice relative to noninjected controls were reduced by 92-98% in MLR and by 2- to 10-fold in IL-2 LDA. In contrast, responses against third-party MHC antigens by either the injected or the noninjected mice were identical. Fifty percent of all mice injected with the T cell lines were tolerant to Mlsa. These results strongly suggest that murine T cells express the Mlsa gene product.

Tolerance to minor histocompatibility antigens

A neonatal tolerance model employing fully allogeneic lymphoid cells as tolerogen was used in an investigation of tolerance to self and donor minor histocompatibility antigens (miHA). Tolerance was assessed by skin grafting and subsequently by the generation of cytotoxic T lymphocytes. Two strain combinations were investigated. In the first, BALB/c-B10, none of the mice became tolerant to H-2d: all gave responses to BALB/c and B10.D2 antigens comparable to uninjected controls. However, tolerance was secured to BALB miHA in the face of reactivity to the original donor cells (i.e., BALB/c), showing that multiple miHA can induce tolerance independently of major histocompatibility complex (MHC) antigens. In the reverse strain combination, in which tolerance to B10 antigens was successfully established in BALB/c recipients, MHC restriction of tolerance to self miHA could not be demonstrated, as mice tolerant to B10 were unresponsive to BALB.B antigens, too. Again, the induction of tolerance to multiple donor miHA proved to be independent of tolerance to donor MHC antigens, and a great deal easier.

Selective resistance of bone marrow-derived hemopoietic progenitor cells to gliotoxin

The fungal metabolite gliotoxin at low concentrations prevents mitogen stimulation of mature lymphocytes as a result of gliotoxin-induced genomic DNA degradation. Bone marrow, on the other hand, contains a subpopulation of cells resistant to gliotoxin at similar concentrations. This population includes the hemopoietic progenitor cells that grow in vitro in response to appropriate colony-stimulating factors and cells that form colonies in the spleens of lethally irradiated recipients. Gliotoxin treatment of lymph node cell-enriched bone marrow significantly delayed the onset of graft-versus-host disease in fully allogeneic bone marrow chimeras.

Presentation of alloantigens by host cells

Presentation of alloantigens by host cells has been examined in vivo by means of a murine cell transfer system. Primary (1 degree) hosts were activated by the i.p. administration of allogeneic spleen cells and their spleen or peritoneal cells were transferred into syngeneic secondary (2 degrees) hosts 3 days later. Sensitization of 2 degrees hosts was assessed by their ability to reject donor strain skin grafts prematurely. The transferred cells were routinely depleted of T lymphocytes. We show that (a) 5 X 10(7) spleen and 3 X 10(6) peritoneal cells consistently caused marked accelerated graft rejection; (b) this effect was antigen specific and observable in all strain combinations studied; (c) it was caused by the active sensitization of 2 degrees hosts, but not by contaminating donor strain cells; (d) the cells involved were plastic adherent and viability was not a requirement; and (e) both class I and II, but not minor, histocompatibility antigens played a role in this model. We conclude that presentation of alloantigens by host antigen-presenting cells can be a potent route of allosensitization.

Abrogation of resistance to bone marrow transplantation by induction of specific tolerance in natural killer cells?

Hybrid resistance describes the capacity of first generation (F1) hybrids between certain mouse strains to inhibit the growth of tumour or haematopoietic cells of parental origin. The cells that appear to mediate this phenomenon differ from classical T and B lymphocytes in several respects. For example, they are unusually radioresistant, show no immunological memory, are present in thymectomized or congenitally athymic mice, are not functional until about 3 weeks after birth. These characteristics suggest that the effectors are natural killer (NK) cells. Although most of the evidence implicating NK cells in hybrid resistance is circumstantial, the experiments of Warner and Dennert are more direct in that they show that resistance can be restored to mice with a congenital or induced defect in NK activity by the infusion of cells belonging to an NK clone. Conversely, treatment of mice with an antibody to NK cells abrogated hybrid resistance to parental bone marrow grafts. Both NK cells and the effectors of hybrid resistance are generally considered to be nonspecific. We have now investigated this assumption by attempting to prevent hybrid resistance by neonatal tolerance induction with parental strain antigens. Our data indicate that hybrid resistance can be abrogated by this means and that the tolerance is specific and transferable with Thy-1+ spleen cells.