Implantation of a foetal thymus, restoring immunological competence in a patient with thymic aplasia (Digeorge's syndrome)

Thymic microenvironment's impact on immunosenescence

Age-related thymic involution is characterized by the loss of T cell development and the supporting epithelial network, which are replaced by adipose tissue. We previously showed that aging functionally impairs lymphohematopoietic progenitor cells, including thymic early T cell progenitors (ETPs), contributing to thymic involution. Considering that the thymic microenvironment is essential for thymocyte incubation, we aimed to investigate its role in age-related thymic involution and the mechanisms underlying these changes. The challenge in studying these processes led us to transplant T cell-depleted fetal thymus tissue into the kidney capsule of aged mice. This model allowed us to identify the mechanisms driving age-related changes in the thymic microenvironment and to assess whether these changes could be reversed. Flow cytometry was used to detect naïve T cells (CD62L+CD44-), including CD4 CD8 double-negative, double-positive, and single-positive T cells. Real-time PCR was used to detect and quantify signal-joint T cell receptor excision circles. We rearranged δRec-ΨJα in murine peripheral blood leukocytes to evaluate the thymic output of newly developed naïve T cells in the mice and gene expression in the thymus. Age-related thymic involution decreased naïve T cells and increased memory T cells, while fetal thymus transplantation improved thymic output and T cell production and reversed the impairment of thymopoiesis due to thymic involution in aged mice. Furthermore, the expression of key cytokines was restored and ETPs in the aged mice showed normal thymic T cell development. Our study suggests that degenerative changes in the thymic microenvironment are the primary cause of thymic dysfunction, leading to immunosenescence associated with age-related thymic involution.

Current status and legal/ethical problems in the research use of the tissues of aborted human fetuses in Japan

To date, there is no law regulating the research use of human aborted fetuses in Japan. The aim was to review the current status with historical background and legal/ethical problems limiting the research use of the tissues of aborted human fetuses. We reviewed literature via PubMed, Web of Science, Scopus, Japana Centra Revuo Medicina and CiNii, reports from various committees and research groups from Ministry of Health, Labour and Welfare (MHLW), and domestic books. Aborted human fetal tissues used for research purposes were first documented in the 1920s. The first guideline, the Peel Code was released in 1972. Since then, in Western countries, the research use of aborted fetuses has been less restricted compared with that of embryos, due to the following guidelines outlined by expert groups. Currently, aborted fetal tissues are commercially available for research purposes in the United States. In Japan, only four indications are presented in "a public statement permitting research use of deceased fetuses' and 'neonates' organs, etc." (1987). In the 2000s, expert committees of the MHLW concluded that research use of human aborted fetuses should be discontinued, and that comprehensive rules and independent regulations should be implemented. This issue has not been discussed in the Japanese legislature since 2003. Establishment of laws and guidelines for this issue is insufficient not only in Japan but also in other countries. It is important to secure transparency for making laws and guidelines and in obtaining public understanding.

Sources of Human Hematopoietic Stem Cells for Transplantation–A Review

Transplantation of hematopoietic stem cells provides a means of replacing a defective hematopoietic system in patients with a wide range of malignant and nonmalignant disorders that affect the blood forming tissue. The same procedure has also allowed dose-escalation of standard chemotherapy and radiotherapy in the treatment of malignant disease of nonhematological origin. Until recently, bone marrow has been the sole source of hematopoietic stem cells, but limitations of conventional bone marrow transplantation have stimulated a search for alternative sources and uses of stem cells. Fetal tissues (especially liver) are a recognized source of transplantable stem cells and offer the great advantage of reduced immunogenicity, potentially removing the problems of tissue type matching. Umbilical cord blood is also a rich source of stem cells and, although it contains alloreactive cells, it is readily available without special ethical constraints. Both fetal tissue and cord blood suffer the disadvantages of limited numbers of stem cells per donation, and there is much interest in the development of technologies for the safe and reliable expansion and/or pooling of stem and progenitor cells. The observation that small numbers of stem cells are found in the peripheral blood of adults has led to the exploitation of the blood as a further source of stem cells. The ability to mobilize these cells from the medullary compartment into the periphery by the use of chemotherapy and/or recombinant hematopoietic growth factors has enabled the collection of sufficient numbers of cells for transplantation purposes. All of these advances are increasing the options and the range of choices available to clinicians and patients in the arena of hematopoietic stem cell transplantation.

Thymus Transplantation

Thymus transplantation was first attempted in the 1960s and 1970s using fetal thymus tissue [1, 2]. The results overall were disappointing [3–6]. In part the poor outcomes related to the lack of reagents needed to characterize and identify the patients into those who were truly athymic (complete DiGeorge anomaly) and those who had bone marrow stem cell problems (severe combined immunodeficiency). It is also possible that the fetal thymus tissue was too small to reconstitute a human infant [7]. The use of fetal thymus carried the risk of fatal graft versus host disease since mature T-cells can be found in the human thymus by the end of the first trimester [3]. By 1986, in a review of 26 infants treated with fetal thymus transplantation, 22 had died; the other 4 patients had achieved a 3-year survival [6].

The fundamental contribution of Robert A. Good to the discovery of the crucial role of thymus in mammalian immunity

Robert Alan Good was a pioneer in the field of immunodeficiency diseases. He and his colleagues defined the cellular basis and functional consequences of many of the inherited immunodeficiency diseases. His was one of the groups that discovered the pivotal role of the thymus in the immune system development and defined the separate development of the thymus-dependent and bursa-dependent lymphoid cell lineages and their responsibilities in cell-mediated and humoral immunity.

Biased T-cell receptor repertoires in patients with chromosome 22q11.2 deletion syndrome (DiGeorge syndrome/velocardiofacial syndrome)

Chromosome 22q11.2 deletion (del22q11.2) syndrome (DiGeorge syndrome/velocardiofacial syndrome) is a common syndrome typically consisting of congenital heart disease, hypoparathyroidism, developmental delay and immunodeficiency. Although a broad range of immunologic defects have been described in these patients, limited information is currently available on the diversity of the T-cell receptor (TCR) variable beta (BV) chain repertoire. The TCRBV repertoires of nine patients with del22q11.2 syndrome were determined by flow cytometry, fragment size analysis of the third complementarity determining region (CDR3 spectratyping) and sequencing of V(D)J regions. The rate of thymic output and the phenotype and function of peripheral T cells were also studied. Expanded TCRBV families were detected by flow cytometry in both CD4+ and CD8+ T cells. A decreased diversity of TCR repertoires was also demonstrated by CDR3 spectratyping, showing altered CDR3 profiles in the majority of TCRBV families investigated. The oligoclonal nature of abnormal peaks detected by CDR3 spectratyping was confirmed by the sequence analysis of the V(D)J regions. Thymic output, evaluated by measuring TCR rearrangement excision circles (TRECs), was significantly decreased in comparison with age-matched controls. Finally, a significant up-regulation in the percentage, but not in the absolute count, of activated CD4+ T cells (CD95+, CCR5+, HLA-DR+), IFN-gamma - and IL-2-expressing T cells was detected. These findings suggest that the diversity of CD4 and CD8 TCRBV repertoires is decreased in patients with del22q11.2 syndrome, possibly as a result of either impaired thymic function and/or increased T-cell activation.

The human pluripotent stem cell: impact on medicine and society

OBJECTIVE

To discuss the current state of the science surrounding human pluripotent stem cells and to show that the derivation of such cells from donated preimplantation human embryos should be eligible for federal funding provided that certain protections are met.

DESIGN

A literature search focusing on the scientific aspects of pluripotent stem-cell research and analyses of current and past legislation and federal panel recommendations.

CONCLUSION(S)

The current federal laws regulating the permission necessary to obtain fetal tissue from elective pregnancy terminations are intended to insulate the decision to terminate a pregnancy from the potential positive influence of fetal tissue transplantation. A similar situation can be created for the derivation of cells from excess preimplantation human embryos produced by IVF programs. If, as in fetal tissue research, assurances can be made that the research will have no influence on the decision to dispose of the embryo, the derivation of pluripotent stem cells from embryo should proceed with federal funding.

Normalization of the peripheral blood T cell receptor V beta repertoire after cultured postnatal human thymic transplantation in DiGeorge syndrome

Complete DiGeorge syndrome is an immunodeficiency disease characterized by thymic aplasia and the absence of functioning peripheral T cells. A patient with this syndrome was transplanted with cultured postnatal human thymic tissue. Within 5 weeks of transplantation, flow cytometry, T cell receptor V beta sequence analysis, and cell function studies showed the presence of oligoclonal populations of nonfunctional clonally expanded peripheral T cells that were derived from pretransplantation T cells present in the skin. However, at 3 months posttransplantation, a biopsy of the transplanted thymus showed normal intrathymic T cell maturation of host T cells with normal TCR V beta expression on thymocytes. By 9 months postransplantation, peripheral T cell function was restored and the TCR V beta repertoire became polyclonal, coincident with the appearance of normal T cell function. These data suggest that the transplanted thymus was responsible for the establishment of a new T cell repertoire via thymopoiesis in the chimeric thymic graft.

Organ culture for thymus transplantation

A method is presented for organ culture of postnatal thymus. Such tissue has been used for transplantation for nearly 20 years, but lasting benefit has been observed only in patients with the DiGeorge anomaly. Transplantation in other diseases has produced little or no results. Recently, improved methods for preparing the tissue as well as modifications of the culture media show marked improvement in quality and quantity of tissue suitable for transplant. In addition, using recently available monoclonal antibodies, preservation of vital stromal components can be monitored. The availability of reasonable amounts of high quality thymus tissue for transplantation may stimulate interest in further clinical trials where thymus transplantation may augment or restore T cell immunity.

Neuromuscular complications of bone marrow transplantation

Six children are reported with neuromuscular complications of allogenic bone marrow transplantation. Myositis occurred in 4, chronic inflammatory demyelinating neuropathy in 1, and myasthenia gravis in 1. Chronic graft-versus-host disease was present in 3. The onset following bone marrow transplant may be delayed.

Human fetal tissue research: practice, prospects, and policy

Tissue from human fetal cadavers has long been used for medical research, experimental therapies, and various other purposes. Research within the last two decades has led to substantial progress in many of these areas, particularly in the application of fetal tissue transplantation to the treatment of human disease. As a result, clinical trials have now been initiated at centers around the world to evaluate the use of human fetal tissue transplantation for the therapy of Parkinson's disease, insulin-dependent diabetes mellitus, and a number of blood, immunological and, metabolic disorders. Laboratory studies suggest a much wider range of disorders may in the future be treatable by transplantation of various types of human fetal tissue. A combination of characteristics renders fetal tissue uniquely valuable for such transplantation, as well as for basic research, the development of vaccines, and a range of other applications. Although substitutes for human fetal tissue are being actively sought, for many of these applications there are at present no satisfactory alternatives. Important issues remain unresolved concerning the procurement, distribution, and use of human fetal cadaver tissue as well as the effects of such use on abortion procedures and incidence. These issues can be addressed by the introduction of appropriate guidelines or legislation, and need not be an impediment to legitimate research and therapeutic use of fetal tissue.

From a historical outline of transplants to the concept of biological ego

A chronology of the biological preliminaries of human transplantation science is proposed together with a chronological listing of the applications which transplants have had in clinical medicine in general and in pediatrics in particular. The most significantly immunological elements which surface from this assortment of experiences (in which those of pediatric interest have a considerable role) contribute easily to a more deeply perceived culture of man's biological individuality.

Prediction of persistent immunodeficiency in the DiGeorge anomaly

To assess the natural history of the immune defect in DiGeorge anomaly, we reviewed serial immunologic studies in 18 patients. The diagnosis was made with criteria based on the concept of the DiGeorge anomaly as a field defect. Initial or early follow-up laboratory examination suggested moderate to normal T cell function in 14 patients. None of these patients have lost T cell capability; they have never had infections characteristic of T cell deficiency. Four patients had clinical and laboratory evidence of profound immunodeficiency. A decreased number of CD4+ cells (less than 400/microliters) and a decrease in phytohemagglutinin responsiveness (stimulation index less than 10) may be useful in discriminating patients with immunodeficiency; absolute lymphocyte count and immunoglobulin values were not informative. At the time of surgery, the thymus was not found in 11 of 14 patients; however, only two of these patients had immunodeficiency. Patients with a persistently low number of CD4+ cells and decreased phytohemagglutinin response are candidates for immunologic reconstitution.

DiGeorge syndrome with hypogammaglobulinaemia: a patient with excess suppressor T cell activity treated with fetal thymus transplantation

A male infant with DiGeorge syndrome had hypogammaglobulinaemia with a normal number of B cells. CD3(+) T cells were reduced and the CD4(+)/CD8(+) ratio was reversed. Proliferative responses of T cells to mitogens and to allogeneic cells were low. The pokeweed mitogen (PWM)-induced B cell differentiation assay revealed a higher than normal suppressor T cell activity. This suggests that some T cells had differentiated into functionally mature cells resulting in an imbalance of regulatory T cell functions and that excess suppressor activity might play a role in hypogammaglobulinaemia. Fetal thymus transplantation improved both cellular and humoral immunity. The patient's susceptibility to viral and bacterial infections, proliferative response of T cells and serum Ig concentration returned to normal. The excess suppressor activity seen before transplantation disappeared. Hypocalcaemia did not improve. These results show that fetal thymus transplantation was effective not only in reconstituting cellular immunity but also in normalizing the imbalance of regulatory T cell functions in this patient with DiGeorge syndrome.

Flow cytometric analysis of lymphocyte subpopulations in infants with congenital heart disease

Premortem diagnosis of the DiGeorge syndrome and its partial variants relies on the demonstration of a primary defect in cell-mediated immunity, generally in the setting of an infant with congenital heart disease, hypocalcemia, absence of a thymic shadow, and typical dysmorphic features. Although T-cell enumeration is considered a vital part of the diagnostic evaluation, no studies to date have addressed the issue of appropriate reference data in infants with congenital heart disease. We therefore undertook a prospective descriptive study of lymphocyte phenotype analysis in 27 nontransfused infants undergoing diagnostic cardiac catheterization. Striking differences were seen between patients and adult controls in means percentages and numbers of most lymphocyte subsets analyzed. Few differences were found in comparing the patient data to values for age-matched control infants without heart disease. The data are discussed with reference to published values for patients with partial DiGeorge syndrome. It is concluded that lymphocyte phenotype analysis in the diagnostic evaluation of patients with suspected DiGeorge syndrome must utilize appropriate reference values.

The DiGeorge syndrome. I. Clinical evaluation and course of partial and complete forms of the syndrome

This study describes clinical signs and symptoms in 16 patients with the DiGeorge syndrome (DGS). Diagnosed on the basis of typical facial stigmata, a broad spectrum of severity is seen with respect to congenital heart disease, hypoparathyroidism and immunologic parameters. A simple index of severity is introduced that clearly differentiates complete forms of the syndrome (cDGS) with poor prognosis from partial forms of the syndrome (pDGS). Of 13 pDGS patients, 12 are still living; 8 underwent corrective heart surgery without infectious complications. Moderate to severe mental retardation is seen in all pDGS patients. Due to the lack of thymus function, immunodeficiency is a result of cDGS, whereas immunoregulatory disturbances (hypergammaglobulinaemia, high titres of specific antibody production) prevail in pDGS patients.

Indications for immunotherapy

Underlying immunodeficiency should be suspected in every patient, irrespective of age, who has recurrent, persistent, severe, or unusual infections. Defects in immunity can be classified into primary or secondary disorders involving specific or nonspecific immune mechanisms. Several forms of primary and secondary immunodeficiency exist for which various immunotherapeutic modalities are available. Significant among these are immunoglobulins commercially available for intravenous infusion. Other therapies include transplantation of tissue such as bone marrow, fetal liver, and fetal thymus. Enzyme replacement therapy is being developed, as is the use of products unique to immunocompetent cells, such as thymus extract, thymosin, interleukins, and transfer factor. Forms of nonspecific immune modulators and stimulators are other possibilities, especially in the context of the immunotherapy of tumors.

Reconstitution of T-cell deficiency by thymic hormone or thymus transplantation therapy

Correction of T-cell defects by either thymic hormone treatment or thymus transplantation has proven to be more difficult clinically than historically anticipated. Because the precise action of thymic hormones is unknown and because these hormones act upon post-thymic cells, therapeutic attempts may fail owing to lack of sufficient substrate population. Results of thymic transplantation suggest that this procedure may be best utilized for the treatment of mild T-cell defects, rather than as complete replacement treatment for severe deficiency. Future clinical trials of thymic transplantation or thymic hormone appear justified in narrowly circumscribed and well-characterized conditions.

Immuno-reconstitution by thymic transplant in DiGeorge's syndrome

Persistent hypocalcaemic tetany in a breast-fed neonate made us suspect DiGeorge's syndrome, particularly as the baby had an abnormal facies, and a ventricular septal defect. Immuno-reconstitution was successfully achieved by thymic transplant. Evidence of immuno-reconstitution on the basis of the histology of the post-transplant thymus has not been previously recorded.

Temporal bone pathology in DiGeorge's syndrome

DiGeorge's syndrome is characterized by partial or complete absence of the parathyroid and thymus glands and is often associated with other developmental anomalies, particularly of the structures arising from the third and fourth pharyngeal pouches. The temporal bone findings in three cases of DiGeorge's syndrome are presented. Patients with this condition have a high incidence of Mondini dysplasia in both ears, sometimes with other anomalies of the external or middle ears. Hearing may range from normal to profound deafness and may manifest sensorineural, conductive, or mixed losses of varying degrees.

Bone marrow transplantation--an expanding approach to treatment of many diseases

Thus, we can conclude that marrow transplantation has already influenced medical practice greatly. It has offered a treatment which often cures patients of more than 20 otherwise lethal diseases. The treatment so horrendously difficult and dangerous at first has already been greatly improved, simplified, and made much safer. The availability of a suitable donor has been much extended and real progress has been made in prevention and perhaps even in treatment of graft-versus-host disease. This has made possible the option of marrow transplantation for every patient in whom we think the treatment may be beneficial. The problem underlying many cases of interstitial pneumonia has been identified and patients are already benefitting clinically from this progress. Progress has also been made which promises antiviral therapy which could reduce, prevent, and ultimately eliminate the intercurrent virus infections which limit the applicability of marrow transplantation, especially for children with severe immunodeficiencies. I do not know how far this line of investigation can be taken. However, just as we have learned stepwise to use marrow transplants from matched siblings to treat many diseases, to use fetal liver in place of bone marrow, to employ matched relative donors when a matched sibling is not available, and, finally, even to use parental donors to achieve correction of SCID, we now have good reason to believe that, ultimately, we can use marrow transplantation without fear of GVHD to address many additional genetically determined and acquired diseases; certainly, for those diseases that involve any of the cells that are derived from bone marrow cells, and perhaps for those attributable even to cells of other organs and tissues, the functions of which are, in whole or in part, a consequence of interactions of marrow-derived cells and cells of ectodermal or endodermal origin, marrow transplantation may be useful. To us, the future of marrow transplantation as a major modality of treatment or prevention of many diseases, including hemoglobinopathesis, immunodeficiencies, hematologic abnormalities, abnormalities of function of marrow-derived cells, and even inborn errors of function of cells of organs and tissues not of marrow origin, seems bright, indeed. Further, with the capacity to introduce resistance genes against viruses and malignancies, autoimmune diseases, and diseases dependent on anomalies of immune response genes, marrow transplantation for many other diseases seems a more remote possibility.(ABSTRACT TRUNCATED AT 400 WORDS)

Thymosin therapy in the DiGeorge syndrome

Reconstruction of the T-cell immune defect in patients with the DiGeorge syndrome has been accomplished in the past by fetal thymus transplantation. Because of the risk of fatal graft-versus-host reaction with fetal thymus transplantation in patients with abnormal T-cell immunity, we have examined the effects of a thymus tissue extract, thymosin fraction 5, on the in vitro and in vivo immune function in children with the DiGeorge syndrome. T-cell numbers were increased with thymosin F5 in vitro in three of five patients. T-cell number and function was improved in three of four patients treated with thymosin F5 in vivo. Spontaneous improvement in the immune function of these patients cannot be excluded. These results suggest, however, that further trials with thymosin F5 therapy may be indicated in patients with the DiGeorge syndrome.

Screening tests for cell-mediated immunodeficiency diseases

As our knowledge of immunology has become more sophisticated we have had to alter our ideas of the etiology of many immune deficiency diseases. Indeed, current concepts now prevalent have led to reclassification of a number of disease entities. In order to keep our diagnostic efforts abreast of the information being generated by the extensive immunology research programs now in progress, the clinical laboratory has been required to offer a new array of sophisticated tests on a relatively routine basis. This article is intended to serve as a brief review of immunobiology and immunodeficiency diseases with an indepth coverage of specialized tests generally available at the large centers. With an understanding of the principles, procedures, and pitfalls of the tests carried out the laboratory scientist is in a better position to assist the clinician in reaching the correct diagnosis. The detailed review is concerned with methods available to separate, classify, and subclassify lymphocytes and thereby allow a categorization of immune deficiency diseases. Toward that end there is a discussion of surface markers, rosetting, mitogenic and antigenic responsiveness as well as lymphokine production. With a view to present day research tests that might eventually find their way into the armamentarium of the clinical laboratory in the future, there is brief discussion of the methods presently used to classify T-cells as helper, suppressor, or effector cells, assays of some of the lymphokines, and measurement of antibody synthesis in cell culture.

Successful restoration of immunity in the DiGeorge syndrome with fetal thymic epithelial transplant

A 13-month-old girl presented with right upper lobe pneumonia and hypocalcaemic seizures: investigations showed hypoparathyroidism and impaired cell-mediated immune responses. Other features of the DiGeorge syndrome included hypertelorism, short philtrum of the lip, right-sided aortic arch, and aberrant origin of the left subclavian artery. Successful restoration of the immunodeficiency was achieved by transplantation of fetal thymic epithelium.

Use of early fetal tissues obtained from suction termination of pregnancy

Organs were identified in the fetal products of pregnancies of short gestation terminated by the suction method. Various tissues from such fetuses were grown in tissue-culture and some of these cultures were used for the isolation of viruses. This new approach would ensure the supply of human embryonic tissue, essential for certain virlogical procedures, as suitable fetuses from pregnancies terminated by hysterotomy become less common. Tissues from these early fetuses could also be used fro transplantation and developmental studies.

Analysis of human thymocyte subpopulations using discontinuous gradients of albumin: precursor lymphocytes in human thymus

Precursor lymphocytes, obtained from human tissue on bovine serum albumin (BSA) gradients followed by removal of sheep erythrocyte (E)-reactive thymocytes on Ficoll, are the predominant lymphoid subpopulation found in young fetal thymuses. This subpopulation shows a progressive decline in relative numbers during fetal life, accompanied by a rise in both the relative and absolute numbers of E-reactive thymocytes. Precursor thymocytes differentiate in vitro to E-reactive cells resembling T cells in their morphology, sedimentation on BSA gradients, and response to phytohemagglutinin. Agents tending to increase intracellular concentrations of cyclic-AMP accelerate the rate of differentiation of precursor cells to lymphocytes which closely resemble T cells.

Constrictive pericarditis, intestinal lymphangiectasia, and reversible immunologic deficiency

A patient with constrictive pericarditis, secondary intestinal lymphangiectasia, and protein-losing enteropathy was demonstrated to have the characteristic immunologic deficiency associated with intestinal lymphangiectasia: hypogammaglobulinemia, lymphocytopenia, cutaneous anergy, impaired allograft rejection. and diminished in vitro lymphocyte proliferative responses. Following surgical correction of the cardiac abnormality, the intestinal lymphangiectasia and protein-losing gastroenteropathy resolved and was accompanied by a slow but progressive return of normal immune function. This documented reversal of the immunologic deficiency in intestinal lymphangiectasia supports the concept that the immune defect in this syndrome is due to the excessive loss of lymphocytes and immunoglobulins into the gastrointestinal tract.