The use of fetal hematopoietic stem cells for in utero transplantation to create permanent hematochimerism represents a new concept in fetal therapy. In one fetus with alpha-thalassemia, one with sickle cell anemia, and one with beta-thalassemia, we have transplanted fetal liver cells obtained from legal abortions in gestational weeks 6-11. The fetus with alpha-thalassemia was transplanted twice during pregnancy, in the 15th (20.4 x 10(8) cells/kg) and in the 31st weeks of gestation (1.2 x 10(8) cells/kg), and is now two years of age. One fetus with sickle cell anemia received its transplant in the 13th week of gestation (16.7 x 10(8) cells/kg), and is now one year old. The fetus with beta-thalassemia was transplanted in 18th week (8.6 x 10(8) cells/kg), and is now three months old. Engraftment was evaluated by chromosomal analysis (sex chromosomes), red cell phenotyping, HLA class I and II typing, and PCR (polymerase chain reaction) for Y chromosome-specific sequences and DNA polymorphisms in cord and peripheral blood. The children with alpha- and beta-thalassemia underwent bone marrow aspirations at 3 and 7 months of age, respectively. In neither of these cases were we able to detect convincing evidence of stem cell engraftment. Thus, the administration of fetal stem cells to fetal recipients after the 12th week of gestation did not result in permanent hematochimerism. It remains to be determined whether the engraftment process can be promoted by earlier transplantations and/or higher cell doses.

Intravenous Immunoglobulin (IVIG) at a concentration of 5 mg/ml, significantly inhibited mitogenic responses to phytohaemagglutinin (PHA), concanavalin A (conA) and pokeweed mitogen (PWM) by peripheral blood cells from healthy donors. No difference in inhibition by IVIG was seen when stimulating different T-lymphocyte cell subsets. Inhibition by IVIG was dose-dependent. An increased response was observed when IVIG was added more than 12 h after PHA compared to adding 1 h before [P = 0.05]. Intravenous immunoglobulin added to mixed lymphocyte cultures (MLC), reduced the median response by more than 60% (range 14-89%; P = 0.03) and almost completely abrogated the lymphocyte response to Staphylococcus aureus protein A (SPA), whose median inhibition was 94% (range 90-99%; P = 0.02). When comparing 12 different commercial IVIG preparations at a concentration of 2.5 mg/ml, the median inhibition of the PHA stimulation ranged from 4% to 35% and the MLC response from 0% to 66%. In the presence of IVIG the lymphocyte response to different herpes virus antigens was reduced by > 50%. No difference in inhibitory effect was seen when comparing IVIG and cytomegalovirus (CMV) hyper Ig, but CMV negative Ig resulted in lower inhibition [P = 0.05]. Three out of five IgG preparations (2.5 mg/ml) made from single donors inhibited PHA stimulation significantly more than commercial IVIG [P < 0.05]. Mean inhibition was 61% compared to 35%. Inhibition by pooled IgG from five donors was 56%. F(ab')2 fragments of IVIG inhibited the MLC response by more than 50% (range 34-75%), SPA stimulation by 97% (83-104%) and PHA stimulation by more than 30% (26-37%). One of two Fc preparations tested had an inhibitory effect, but the inhibition was less than that obtained with the F(ab')2 fragments [P = 0.04]. These results further strengthen the notion that IVIG exerts its immune modulatory effect by binding to leukocyte surface receptors. A clear inhibition was obtained with concentrations corresponding to the serum levels obtained when IVIG is given 250-500 mg/kg bodyweight. F(ab')2 fragments have the same inhibitory effect as intact IgG molecules but the role of Fc fragments still remains unclear. Differences in the immunosuppressive effect of various IVIG preparations may be associated with the method of preparation.

Summary:The use of hematopoietic stem cells for in utero transplantation to create permanent hematochimerism represents a new concept in fetal therapy, although this approach has provided heterogeneous results. In this paper we have undertaken molecular, phenotypic and functional studies aimed at identifying the presence of fully competent T lymphocytes in samples of fetal livers and cord blood. We found mature VDJ TCR ␤ chain transcripts in fetal liver cells taken from 7 to 16 weeks of gestation and a similar pattern was detected in cord blood cells sampled from 13.5 to 20.5 weeks of gestation. A V␤8 gene sequence comparable to that detected in adult PBMC was found in fetal liver samples at 9 or 17 weeks gestation. PreT␣ message was detected in all samples and its expression decreased in fetal blood samples with increasing gestational age while C␣ message appeared at 9.4 weeks and its expression increased during gestational age. T cell clones obtained from fetal liver cells showed a mature TCR ␣␤ + , CD8 + phenotype and displayed strong alloreactivity against allo-MHC class I molecules. The presence of alloreactive T lymphocytes may explain the failure to engraft in fetuses older than 13 to 16 weeks and may provide insights into fetal liver transplantation. Bone Marrow Transplantation of gestation have been transplanted into fetuses at the 13th to 18th week of gestation. 6-8 Considerably better results have been obtained in fetuses affected by immunodeficiency syndromes such as SCID or Bare Lymphocyte diseases. 1,9 These findings raise the possibility that the fetus may develop an allogeneic immune reaction responsible for graft failure. Accordingly, fetal liver HSC were capable of engraftment in syngeneic, but not allogeneic recipient mice, 10 and successful allogeneic in utero transplantation of fetal HSC in sheep and monkeys occurred if both the donor and recipient fetuses were in a preimmune status. 5 Furthermore, we have recently reported 7 that in utero transplantation of an 18 week fetus with fetal HSC resulted in graft failure and after birth the recipient had a very high cytotoxic T cell precursor (CTLp) frequency against donor cells, thus indicating that generation of an alloimmune response rather than tolerance induction was the effect of the procedure.The development of T lymphocytes starts primarily in the embryonic thymus 11-13 after 8 weeks gestation, where they undergo a complex series of differentiation events leading to the expression of the T cell receptor (TCR) complex. 14 Efficient performance of this program appears to be dependent on cellular interactions between developing thymocytes and thymic stromal components. 15 These cells may then colonize the periphery, including the fetal liver itself, as the presence of phenotypically mature T cells has been demonstrated in 11-13 to 22 week old fetal livers. 16 Moreover, recent studies have shown that the liver is also a site for extrathymic T cell development and maturation. 17 Against this background, we have undertaken molecular, phenotypic ...

Most women seeking abortion seem to be in favor of the idea of fetal tissue donation for the treatment of other fetuses. The possibility of obtaining fetal liver tissue and the number of fetal stem cells retrieved are closely correlated to gestational age. A tissue bank appears to facilitate the operation of a fetal to fetal stem cell transplantation program.

Objective: In order to study the immunological function of the human fetus in the first and second trimesters, mixed lymphocyte culture (MLC) of fetal liver and thymic cells was performed. MLC is a functional test to determine human lymphocyte antigen-D incompatibilities. Methods: Human fetal liver and thymic tissue was obtained from abortions in gestational weeks 7–17.5. Forty-seven fetuses were studied with one-way MLC. The cells were stimulated by adding irradiated fetal liver cells, adult bone marrow and peripheral blood lymphocytes. The activity was measured as DNA incorporation of radiolabeled thymidine. Results: The results indicate that the human fetus is competent to react as early as 11–12 weeks of gestation and in some cases even earlier. In very immature fetal livers (< 8 weeks), the MLC seems to be inhibited. Conclusions: Our data suggest that the human fetus can react against foreign transplantation antigens earlier than previous papers have claimed. The onset of reactivity seems to differ considerably among fetuses. The present findings may explain some of the limited success of in utero transplantations of hematopoietic stem cells in human fetuses of normal immunological status.