Production of fetal antigen-bearing erythrocytes in irradiated adult mice grafted with fetal liver hematopoietic cells.

The production of erythrocytes bearing an "immature" antigen (Im+ cells) and a "fetal" antigen (Ft+ cells) has been studied in irradiated adult mice grafted either with fetal liver or adult bone marrow cells. The Im+ cells reach a peak 8-11 days after grafting. Ft+ cells are detected only after graft of fetal liver cells; the younger the liver, the greater the number. Since Ft+ cells are rapidly and briefly produced, they could be the progeny of erythroid-committed precursors, which are particularly numerous among fetal liver cells. Environmental factors directing the erythropoietic differentiation towards Ft+ erythrocytes in fetuses or Ft- erythrocytes in adults are proposed.     

Development of intraepithelial T lymphocytes in the intestine of irradiated SCID mice by adult liver hematopoietic stem cells from normal mice

BACKGROUND/AIMS: We recently reported the adult mouse liver to contain c-kit+ stem cells that can give rise to multilineage leukocytes. This study was designed to determine whether or not adult mouse liver stem cells can generate intraepithelial T cells in the intestine as well as to examine the possibility that adult liver c-kit+ stem cells originate from the fetal liver. METHODS: Adult liver mononuclear cells, bone marrow (BM) cells, liver c-kit+ cells or bone BM c-kit+ cells of BALB/c mice were i.v. transferred into 4 Gy irradiated CB17/-SCID mice. In other experiments, fetal liver cells from Ly5.1 C57BL/6 mice and T cell depleted adult BM cells from Ly5.2 C57BL/6 mice were simultaneously transferred into irradiated C57BL/6 SCID mice (Ly5.2). At 1 to 8 weeks after cell transfer, the SCID mice were examined. RESULTS: Not only BM cells and BM c-kit+ cells but also liver mononuclear cells and liver c-kit+ cells reconstituted gamma delta T cells, CD4+ CD8+ double-positive T cells and CD8 alpha+beta- T cells of intestinal intraepithelial lymphocytes of SCID mice. Injection of a mixture of fetal liver cells from Ly5.1 C57BL/6 mice and adult BM cells from Ly5.2 C57BL/6 mice into Ly5.2 C57BL/6 SCID mice induced both Ly5.1 and Ly5.2 T cells, while also generating c-kit+ cells of both Ly5.1 and Ly5.2 origins in the liver. CONCLUSIONS: Adult mouse liver stem cells were able to generate intestinal intraepithelial T cells of the SCID mice, and it is thus suggested that some adult liver stem cells may indeed be derived from the fetal liver.     

Fetal to adult hemopoietic cell transplantation in humans: insights into hemoglobin switching

A 2-year-old boy with refractory acute leukemia (ALL) was transplanted with liver cells from twin fetuses of an 18-gestational-week age. Regeneration of hemopoietic cells was evident during the second week following transplantation when a cellular, predominantly erythroid, marrow was present. Studies of bone marrow and peripheral blood cells obtained 21 days posttransplant showed that bone marrow and peripheral blood BFU-E-derived erythroblasts displayed typical fetal patterns of globin chain synthesis (gamma/gamma + beta ratios: 0.87 to 0.98). In addition, all of the individually analyzed erythroid clones displayed a fetal type of globin program, suggesting that the presence of rare, partially switched clones was unlikely. Additional evidence supported the fetal phenotype of these progenitors. The il expression of culture-derived erythroblasts was typical for fetal erythroid cells. As in fetal cells, fetal sheep serum influenced neither the globin nor the il phenotypes, and the growth characteristics were as those observed in fetal liver cultures. That these fetal progenitors matured in vivo and produced cells with a fetal program was shown by the pattern of globin biosynthesis in bone marrow cells and peripheral blood reticulocytes (gamma/gamma + beta ratios: 0.85 to 0.95) at days 14 and 21 posttransplantation. These results indicate that the transplanted fetal cells, in spite of their proliferation and differentiation in the environment of the recipient, continued to express during the early posttransplantation period fetal patterns of globin, surface antigenic determinants, and growth and response to environmental modulation. The observations in this patient support the notion that hemoglobin switching is primarily controlled by a mechanism intrinsic to the stem cell.     

Disruption of palladin leads to defects in definitive erythropoiesis by interfering with erythroblastic island formation in mouse fetal liver

Palladin was originally found up-regulated with NB4 cell differentiation induced by all-trans retinoic acid. Disruption of palladin results in neural tube closure defects, liver herniation, and embryonic lethality. Here we further report that Palld(-/-) embryos exhibit a significant defect in erythropoiesis characterized by a dramatic reduction in definitive erythrocytes derived from fetal liver but not primitive erythrocytes from yolk sac. The reduction of erythrocytes is accompanied by increased apoptosis of erythroblasts and partial blockage of erythroid differentiation. However, colony-forming assay shows no differences between wild-type (wt) and mutant fetal liver or yolk sac in the number and size of colonies tested. In addition, Palld(-/-) fetal liver cells can reconstitute hematopoiesis in lethally irradiated mice. These data strongly suggest that deficient erythropoiesis in Palld(-/-) fetal liver is mainly due to a compromised erythropoietic microenvironment. As expected, erythroblastic island in Palld(-/-) fetal liver was found disorganized. Palld(-/-) fetal liver cells fail to form erythroblastic island in vitro. Interestingly, wt macrophages can form such units with either wt or mutant erythroblasts, while mutant macrophages lose their ability to bind wt or mutant erythroblasts. These data demonstrate that palladin is crucial for definitive erythropoiesis and erythroblastic island formation and, especially, required for normal function of macrophages in fetal liver.     

Rationale for combined use of fetal liver and thymus for immunological reconstitution in patients with variants of severe combined immunodeficiency

Bone marrow cells from a patient with severe combined immunodeficiency were studied in vitro for thymus-dependent lymphocyte (T cell) differentiation by using, at varying times, thymic epithelial monolayers and culture supernatants, thymopoietin, ubiquitin, and thymic extract as inducing agents. On initial evaluation, with thymopoietin or human thymic extract, only a partial differentiation of marrow cells was achieved into cells bearing the human T cell antigenicity without the capacity to form rosettes with sheep erythrocytes, suggesting that the stem cells were defective. Two fetal liver transplantations aimed at reconstitution were unsuccessful, despite evidence of chimerism. Induction studies at that time demonstrated rosetting capacity (with sheep erythrocytes) of the patient's bone marrow cells after coculture with thymic epithelial monolayers but not with their supernatants. An 18-week fetal thymus (irradiated) was then transplanted, but the transplantation was unsuccessful and no clear evidence of chimerism was demonstrated. Subsequently, transplantation of another fetal liver resulted in chimerism and immunologic reconstitution. Serum thymic factor activity rose from 1:2 before transplantation to 1:16 after reconstitution. The combined use of fetal thymus and liver may provide effective immunological reconstitution in some variants of severe combined immunodeficiency.     

Differential reactivities of fetal and adult human erythrocytes to antisera directed against glycolipids of human erythrocytes

Summary. The immunological reactivities of fetal and adult erythrocytes to antisera which were directed against globoside, hematoside and lactosylceramide were compared. Fetal erythrocytes showed higher reactivity than adult erythrocytes in agglutination, hemolysis and absorption capacity of antibody when tested with anti-globoside and anti-hematoside. No differential reactivity was found when tested with anti-lactosylceramide. Treatment of adult erythrocytes by trypsin or by neuraminidase resulted in an increase in their reactivity to the same level as that of fetal erythrocytes, but the reactivity of fetal erythrocytes was not greatly affected by enzyme treatment. The results indicate that globosidie and hematosidie groupings of fetal cells are directly exposed on the periphery of cells, while those of mature erythrocytes are masked by ‘sialomucopeptidyl’ groupings, and their reactivities are hampered.     

Functional differences between transplantable human hematopoietic stem cells from fetal liver, cord blood, and adult marrow.

The purpose of this study was to develop a simple assay for quantitating transplantable human lymphomyeloid stem cells (competitive repopulating units [CRU]) to enable comparison among the numbers and types of progeny generated in NOD/ SCID mice by such cells from different ontologic sources. Sub-lethally irradiated NOD/SCID mice were transplanted with varying numbers of CD34+ cell-enriched suspensions of human fetal liver, cord blood, or adult marrow cells. The types and numbers of human cells present in the marrow of the mice were measured 6 to 8 weeks later using flow cytometry, in vitro progenitor assays, and secondary transplant endpoints. Frequencies of human CRU obtained by limiting dilution analysis of mice repopulated 6 to 8 weeks posttransplant were the same when the lymphoid and myeloid progeny of CRU were both detected by specific immunophenotypic endpoints as when in vitro myeloid progenitor assays were used to detect CRU myelopoietic activity. The average output per injected CRU of very primitive cells (CD34(+)CD38(-) cells, LTC-IC, and secondary CRU) was found to be highest for fetal liver CRU and progressively decreased (up to >100-fold) for ontologically older CRU. In contrast, the average output of mature cells was highest for cord blood CRU and lowest for fetal liver CRU, despite equivalent production of intermediate progenitors. Differences in the relative numbers of mature lymphoid, myeloid, and erythroid progeny produced by CRU from different ontologic sources were also seen. Finally, evidence of a transplantable human lymphoid-restricted cell present throughout ontogeny was obtained. A simpler and easier assay for enumerating transplantable human stem cells with lymphomyeloid reconstituting activity has been described, and its specificity and sensitivity validated. The use of this assay has revealed ontogeny-associated differences in a variety of functional attributes of human stem cells proliferating and differentiating in an in vivo, but xenogeneic, setting.     

The purification and characterization of fetal liver hematopoietic stem cells.

Thy-1loSca-1+Lin-Mac-1+CD4- cells have been isolated from the livers of C57BL-Thy-1.1 fetuses. This population appears to be an essentially pure population of hematopoietic stem cells (HSC), in that injection of only six cells into lethally irradiated adult recipients yields a limit dilution frequency of donor cell-reconstituted mice. Sixty-seven to 77% of clones in this population exhibit long-term multilineage progenitor activity. This population appears to include all long-term multilineage reconstituting progenitors in the fetal liver. A high proportion of cells are in cycle, and the absolute number of cells in this population doubles daily in the fetal liver until 14.5 days postcoitum. At 15.5 days postcoitum, the frequency of this population falls dramatically. Long-term reconstituting HSC clones from the fetal liver give rise to higher levels of reconstitution in lethally irradiated mice than long-term reconstituting HSC from the bone marrow. The precise phenotypic and functional characteristics of HSC vary according to tissue and time during ontogeny.     

Protective immunity against malaria: cellular changes in the liver vary according to the method of immunization

Characterization of cells present in the extravascular compartment of murine liver was performed after different immunization procedures against the malaria parasite Plasmodium yoelii. Mice were immunized with live or irradiated sporozoites or with parasitized erythrocytes. Whatever the immunization protocol used, the mice were protected against a sporozoite challenge but each immunization procedure induced a specific profile of cell types. Immunization with irradiated sporozoite induce a significant increase in CD8+ lymphocytes, parasitized erythrocytes stimulates production of monocytes/macrophages and CD8+ lymphocytes while, after live sporozoites immunization, polymorphonuclear cells, macrophages/ monocytes, B cells and a range of T cell subsets were increased in number.     

A monoclonal antibody against an erythrocyte ontogenic antigen identifies fetal and adult erythroid progenitors

A murine monoclonal antibody (MoAb) designated FA6-152 has been obtained by immunizing mice with fetal erythrocytes. This antibody agglutinates fetal but not adult erythrocytes. Among blood cells, this antibody bound to both adult and fetal monocytes, platelets, and reticulocytes, but did not react with lymphocytes and granulocytes. Fluorescent labeling of marrow cells and of in vitro BFU-E, CFU-GM, and CFU-MK-derived colonies has shown that the antigen defined by FA6-152 MoAb was absent from the granulocytic precursors and was detected on the megakaryocytic lineage at a later stage of differentiation than the platelet-specific markers. In contrast, the antigen appeared as a very early marker of the erythroid differentiation since all erythroblasts, including proerythroblasts, were labeled even before the expression of glycophorin A. Cells from adult marrow and fetal liver were sorted with the FA6-152 MoAb and studied by electron microscopy and cell culture. The negative fraction contained granulocytic, monocytic, and megakaryocytic precursors, whereas the positive fraction was devoid of these precursors and contained monocytes, erythroblasts at all stages of maturation, and a homogeneous population of blasts. Cultures have shown that the only hematopoietic progenitors present in this positive fraction were CFU-E and some BFU-E. The antigenic density was related to the differentiation stage of the erythroid progenitors. In conclusion, this antibody is similar to the previously described 5F1 MoAb (Bernstein and Andrews, J Immunol 128:876, 1982; and Andrews et al, Blood 62:124, 1983) and provides a useful probe for studies leading to improved understanding of normal and malignant erythroid differentiation.     

Fetal haemopoietic cells display enhanced migration across endothelium

Fetal haemopoietic cells continually circulate and migrate into tissues, and thus may have specialized homing capabilities. In this study we investigated the in vitro features of haemopoietic cells in fetal blood and liver which are relevant to homing and engraftment. Fetal cells were examined for long-term culture-initiating cell (LTC-IC) and progenitor content, adhesion molecule expression, cell cycle behaviour and transendothelial migratory activity. The LTC-IC content of fetal CD34+ cells is similar to that of CD34+ cells from cord and adult mobilized blood. In contrast to adult and cord blood CD34+ cells, fetal CD34+ cells were actively cycling (11.0 +/- 1.7% and 28 +/- 1.1% of fetal blood and liver CD34+ cells, respectively, in S+G2M, P < 0.001, compared with cord and adult cells). The striking finding was that fetal haemopoietic cells (both LTC-ICs and committed progenitors) displayed significantly higher levels of migration across endothelium (P < 0.05 compared with cord, P < 0.01 compared with adult blood and bone marrow CD34+ cells), which were further increased by chemokines and growth factors. The superior migratory activity of fetal haemopoietic cells may underlie a more efficient homing ability, in keeping with their physiological role.     

Erythroid differentiation of fetal, newborn and adult haemopoietic stem cells.

Erythroid regeneration was studied in lethally irradiated mice given transplants containing equivalent numbers of haemopoietic stem cells (i.e. CFU) from fetal liver, neonatal marrow or adult marrow. Adult marrow was taken from normal control mice, whose CFU for the most part were not in active cell cycle, as well as from phenylhydrazine-treated groups whose CFU were in similar state of proliferation (i.e. approximately 40-50% in DNA SYNTHESIS) AS THOSE DERIVED FROM FETAL LIVER AND NEONATAL MARROW. Splenic and femoral radioiron (59Fe) incorporation were measured at intervals after transplantation and were found to begin earliest in mice given fetal liver, then in animals given neonatal marrow and latest in recipients of adult marrow. Peripheral reticulocytes showed a similar pattern of recovery. The data reported herein suggest that the differences in erythroid regeneration evoked by transplants of fetal liver, neonatal marrow or adult marrow, are not solely attributed to the degree of proliferation in the pluripotential stem cell compartment. These data may, however, suggest a shorter doubling time for cells comprising the fetal and newborn committed erythroid compartments.     

In vitro generation of hematopoietic stem cells from an embryonic stem cell line.

Hematopoietic stem cells (HSC) are unique in that they give rise both to new stem cells (self-renewal) and to all blood cell types. The cellular and molecular events responsible for the formation of HSC remain unknown mainly because no system exists to study it. Embryonic stem (ES) cells were induced to differentiate by coculture with the stromal cell line RP010 and the combination of interleukin (IL) 3, IL-6, and F (cell-free supernatants from cultures of the FLS4.1 fetal liver stromal cell line). Cell cytometry analysis of the mononuclear cells produced in the cultures was consistent with the presence of PgP-1+ Lin- early hematopoietic (B-220- Mac-1- JORO 75- TER 119-) cells and of fewer B-220+ IgM- B-cell progenitors and JORO 75+ T-lymphocyte progenitors. The cell-sorter-purified PgP-1+ Lin- cells produced by induced ES cells could repopulate the lymphoid, myeloid, and erythroid lineages of irradiated mice. The ES-derived PgP-1+ Lin- cells must possess extensive self-renewal potential, as they were able to produce hematopoietic repopulation of secondary mice recipients. Indeed, marrow cells from irradiated mice reconstituted (15-18 weeks before) with PgP-1+ Lin- cell-sorter-purified cells generated by induced ES cells repopulated the lymphoid, myeloid, and erythroid lineages of secondary mouse recipients assessed 16-20 weeks after their transfer into irradiated secondary mice. The results show that the culture conditions described here support differentiation of ES cells into hematopoietic cells with functional properties of HSC. It should now be possible to unravel the molecular events leading to the formation of HSC.     

Hematopoietic repopulation of adult mice with beta-thalassemia

Deletion of the murine beta-major globin gene on chromosome 7 causes a severe, hypochromic anemia in homozygous mice. We show that over 50% of the homozygous mice die either in utero or at birth. Mice heterozygous for the deletion have a slightly increased percentage of reticulocytes when compared with normal mice, but no clinical anemia. As a therapeutic measure, we transplanted 2 x 10(6) congenic genetically marked normal (+/+) marrow cells into adult homozygous and control heterozygous mice. Pretreatment with marrow ablative irradiation was required to obtain significant percentages of donor peripheral blood cells in the homozygous mice. Red blood cell (RBC) counts normalized after pretransplantation irradiation of thalassemic mice with nonlethal doses as low as 400 R. The thalassemic mice irradiated with 200, 400, and 600 R were erythroid-cell chimeras and remained so for at least 8 months posttransplantation, whereas those irradiated with 800 R had primarily donor erythrocytes by 8 weeks. RBC replacement preceded non- erythroid cell replacement at 200, 400, and 600 R. This selective repopulation was more noticeable in the thalassemic mice than in control mice. The fact that chimeric mice are cured, coupled with a recent observation by others that erythroid replacement occurs in unirradiated newborn thalassemic mice, suggest transplantation therapy in utero might augment survival.     

Antitumor Immunity Induced by Irradiated Tumor Cells Producing Macrophage Colony-Stimulating Factor

We previously reported that administration into mice of mouse lymphoid leukemia L1210 cells engineered to secrete macrophage colony-stimulating factor (M-CSF) could lead to tumor rejection. Here, we demonstrate that inoculation with irradiated M-CSF-producing cells protects mice against a subsequent challenge with unmodified parental tumor cells. We used 2 experimental protocols: the inoculation with irradiated M-CSF-producing L1210 cells (EM5) before the challenge with parental cells and after the challenge with parental cells. Both protocols effectively improved the survival rate of mice compared with protocols in which irradiated non-M-CSF-producing L1210 cells (EM-mock) were inoculated. Inoculation with 1 x 10(2) irradiated EM5 cells was sufficient to prolong the survival time of mice subsequently challenged with 1 x 10(4) parental cells. In vivo depletion experiments with administration of antibodies suggested the involvement of CD4+ T cells, CD8+ T cells, and natural killer (NK) cells in the antitumor effect. Consistent with these findings, the cytotoxic T lymphocyte activity of splenocytes from EM5-inoculated mice was higher than that from EM-mock-inoculated mice, and L1210 tumors were heavily infiltrated by CD4+ T cells and NK cells as well as macrophages in EM5-inoculated mice.     

Normal glutathione content and some related enzyme activities in the fetal erythrocytes

Pure fetal blood was obtained by direct-vision fetoscopy from 66 fetuses at 17-24 weeks gestation. The concentration of GSH and the activities of the enzymes gamma-glutamylcysteine synthetase (GCS), glutathione synthetase (GS), glutathione reductase (GR) and glutathione peroxidase (GPx) were analysed by established techniques to find the normal ranges for this gestational age. The ranges were relatively narrow and could serve as reference values for the prenatal diagnosis of defects in the GSH metabolism of erythrocytes. The results were compared with those obtained from 38 normal adults and with published values on neonatal blood. In the case of GR a comparison was also made with maternal blood. In comparison with adults, fetal erythrocytes showed higher GSH concentration and GCS activity and lower GS and GPx activities. This pattern resembled that found in neonatal erythrocytes except for the GCS activity, which was higher in the fetal cells. Furthermore the differences between fetal and adult erythrocytes were more pronounced than those between neonatal and adult cells. The GR activity of fetal erythrocytes was also higher than that of either normal adult or maternal blood. This difference, however, was reduced to an insignificant level when the enzyme was activated in vitro by flavin adenine dinucleotide (FAD) because of a relatively low per cent activation of the GR in the fetal erythrocytes.     

Allogenic fetal liver cells have a distinct competitive engraftment advantage over adult bone marrow cells when infused into fetal as compared with adult severe combined immunodeficient recipients

In utero transplantation (IUT) is becoming a viable option for the treatment of various immune and metabolic disorders diagnosed early in gestation. In this study, donor fetal liver cells had a 10-fold competitive engraftment advantage relative to adult bone marrow in allogeneic fetal severe combined immunodeficient (SCID) recipients compared with adult recipients. In contrast, adult bone marrow cells engrafted slightly better than fetal liver cells in allogeneic adult SCID transplant recipients. By using different ratios of fetal and adult cell mixtures, fetal liver cells repopulated 8.2 times better than adult bone marrow cells in fetal recipients, but only 0.8 times as well in adult recipients. Fetal SCID recipients were more permissive to an allogeneic donor graft than adult recipients. These data indicate that the recipient microenvironment may regulate the engraftment efficiency of a given stem cell source and suggest that the use of cord blood should be tested in clinical IUT.     

Expression of latent hematopoietic progenitor cells in cultures of newborn and adult baboon liver

The anatomic site of hematopoiesis changes during fetal development from the yolk sac to the liver and finally to the marrow. Factors controlling this switch in the site of hematopoiesis are unknown. We assayed erythroid colony (CFU-E) and erythroid burst (BFU-E) formation in fetal, newborn, and adult baboon liver and marrow to determine the growth requirements of primate hematopoietic progenitor cells from different anatomic sites and developmental stages. We cocultured fetal, newborn, and adult liver and marrow nonadherent cells with adherent cells from these organs to assess the role adherent cells may play in determining the site of hematopoiesis. Fetal liver, fetal marrow, newborn marrow, and adult marrow cultures formed CFU-E and BFU-E colonies in vitro. In contrast, newborn and adult liver cell cultures very rarely formed colonies. However, when newborn or adult liver nonadherent cells were cocultured with marrow adherent cells, CFU-E and BFU-E colonies were detected. The colonies that formed in the newborn and adult liver cultures were derived from the liver and not from the marrow cells or peripheral blood trapped in the liver. These data suggest that in contrast to fetal liver, newborn and adult liver may not be hematopoietic organs in normal primates in vivo because of changes in the growth requirements of hematopoietic progenitor cells present in these organs.     

Adherence of human immunodeficiency virus-infected lymphocytes to fetal placental cells: a model of maternal --> fetal transmission.

The precise timing and mechanism of in utero human immunodeficiency virus (HIV) infection are unknown, but transplacental transmission is likely. Term placentas from HIV+ pregnancies contain only rare HIV-infected cells whose origins and phenotypes remain controversial, and no correlation has been found between the presence of HIV in term placentas and transmission to offspring. Reports of trophoblast infectibility have not been reproducible and do not address the question of infection in the placental stroma, the cells in direct contact with fetal circulation. We report that primary cultures of fetal placental chorionic villus stromal cells, while not infectable in vitro, do support lethally irradiated HIV-infected peripheral blood mononuclear cells (PBMCs) in a form that permits rescue of HIV by activated PBMCs weeks later. Infected PBMCs adhere and become intimately associated with placental cells by a mechanism that is LFA-1 and CD4 independent but can be blocked by antibodies or soluble CD4 binding to cell surface-expressed HIV envelope. The ability to sustain infected irradiated cells was not shared by several trophoblast, fibroblast, or epithelial cell lines. This model has several features that are compatible with in utero transmission and allow testing of various agents proposed as interventions to block maternal-->fetal transmission. Placental stromal cells appear to inhibit apoptosis of HIV-infected, irradiated lymphocytes.