An unusual concurrence of graft versus host disease caused by engraftment of maternal lymphocytes with DiGeorge anomaly

Congenital Athymia: Genetic Etiologies, Clinical Manifestations, Diagnosis, and Treatment

Congenital athymia is an ultra-rare disease characterized by the absence of a functioning thymus. It is associated with several genetic and syndromic disorders including FOXN1 deficiency, 22q11.2 deletion, CHARGE Syndrome (Coloboma, Heart defects, Atresia of the nasal choanae, Retardation of growth and development, Genitourinary anomalies, and Ear anomalies), and Complete DiGeorge Syndrome. Congenital athymia can result from defects in genes that impact thymic organ development such as FOXN1 and PAX1 or from genes that are involved in development of the entire midline region, such as TBX1 within the 22q11.2 region, CHD7, and FOXI3. Patients with congenital athymia have profound immunodeficiency, increased susceptibility to infections, and frequently, autologous graft-versus-host disease (GVHD). Athymic patients often present with absent T cells but normal numbers of B cells and Natural Killer cells (T-B+NK+), similar to a phenotype of severe combined immunodeficiency (SCID); these patients may require additional steps to confirm the diagnosis if no known genetic cause of athymia is identified. However, distinguishing athymia from SCID is crucial, as treatments differ for these conditions. Cultured thymus tissue is being investigated as a treatment for congenital athymia. Here, we review what is known about the epidemiology, underlying etiologies, clinical manifestations, and treatments for congenital athymia.

Maternal microchimerism in pediatric inflammatory bowel disease

Inflammatory bowel disease (IBD) shares many immunologic and clinical characteristics with graft versus host disease caused by allogeneic T lymphocytes after hematopoietic cell transplantation. Since maternal cells are known to enter the fetal circulation in a high proportion of pregnancies, we hypothesized that maternal engraftment in the fetus results in immune sequelae that can lead to IBD.

METHOD

The presence and extent of maternal microchimerism in tissues and blood samples from patients with Crohn's, Ulcerative colitis (UC), and control groups were determined using kinetic Polymerase Chain Reaction (kPCR) to detect maternal- and patient-specific HLA types. In addition, fluorescent in situ hybridization (FISH) was employed to detect maternal cells in biopsies from patients with IBD.

RESULTS

Using kPCR, maternal microchimerism was observed in 9 of the 16 (56%) patients with IBD and 6 out of 15 of the control group (40%) (P=NS). Five of 10 Crohn's patients had evidence of maternal microchimerism (50%) (P=NS). Four of six UC patients had evidence of maternal microchimerism in gut tissues (67%) (P=NS). There was no correlation between maternal michrochimerism and disease activity, disease location or granulomas in patients with IBD. Using FISH, five male Crohn's and five male UC patient's intestinal biopsies were analyzed for maternal microchimerism. No maternal cells were identified.

CONCLUSION

There is nothing in the data to suggest that patients with IBD differ from disease controls in their frequency of maternal microchimerism in either blood or gut mucosal tissues. These data suggest that maternal microchimerism in blood and biopsies is a relatively common phenomenon that has neither positive nor negative impact on IBD.

Immunodeficiency in DiGeorge Syndrome and Options for Treating Cases with Complete Athymia

The commonest association of thymic stromal deficiency resulting in T-cell immunodeficiency is the DiGeorge syndrome (DGS). This results from abnormal development of the third and fourth pharyngeal arches and is most commonly associated with a microdeletion at chromosome 22q11 though other genetic and non-genetic causes have been described. The immunological competence of affected individuals is highly variable, ranging from normal to a severe combined immunodeficiency when there is complete athymia. In the most severe group, correction of the immunodeficiency can be achieved using thymus allografts which can support thymopoiesis even in the absence of donor-recipient matching at the major histocompatibility loci. This review focuses on the causes of DGS, the immunological features of the disorder, and the approaches to correction of the immunodeficiency including the use of thymus transplantation.

Hypomorphic Janus kinase 3 mutations result in a spectrum of immune defects, including partial maternal T-cell engraftment

BACKGROUND

Mutations in Janus kinase 3 (JAK3) are a cause of severe combined immunodeficiency, but hypomorphic JAK3 defects can result in a milder clinical phenotype, with residual development and function of autologous T cells. Maternal T-cell engraftment is a common finding in infants with severe combined immunodeficiency but is not typically observed in patients with residual T-cell development.

OBJECTIVE

We sought to study in detail the molecular, cellular, and humoral immune phenotype and function of 3 patients with hypomorphic JAK3 mutations.

METHODS

We analyzed the distribution and function of T and B lymphocytes in 3 patients and studied the in vitro and in vivo responses of maternal T lymphocytes in 1 patient with maternal T-cell engraftment and residual production of autologous T lymphocytes.

RESULTS

B cells were present in normal numbers but with abnormal distribution of marginal zone-like and memory B cells. B-cell differentiation to plasmablasts in vitro in response to CD40 ligand and IL-21 was abolished. In 2 patients the T-cell repertoire was moderately restricted. Surprisingly, 1 patient showed coexistence of maternal and autologous T lymphocytes. By using an mAb recognizing the maternal noninherited HLA-A2 antigen, we found that autologous cells progressively accumulated in vivo but did not compete with maternal cells in vitro.

CONCLUSION

The study of 3 patients with hypomorphic JAK3 mutations suggests that terminal B-cell maturation/differentiation requires intact JAK3 function, even if partially functioning T lymphocytes are present. Maternal T-cell engraftment can occur in patients with JAK3 mutations despite the presence of autologous T cells.

Immunological aspects of 22q11.2 deletion syndrome

Chromosome 22q11 deletion is the most common chromosomal deletion syndrome and is found in the majority of patients with DiGeorge syndrome and velo-cardio-facial syndrome. Patients with CHARGE syndrome may share similar features. Cardiac malformations, speech delay, and immunodeficiency are the most common manifestations. The immunological phenotype may vary widely between patients. Severe T lymphocyte immunodeficiency is rare-thymic transplantation offers a new approach to treatment, as well as insights into thymic physiology and central tolerance. Combined partial immunodeficiency is more common, leading to recurrent sinopulmonary infection in early childhood. Autoimmunity is an increasingly recognized complication. New insights into pathophysiology are reviewed.

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].

Immunodeficiency and autoimmunity in 22q11.2 deletion syndrome

22q11.2 deletion syndrome is the commonest chromosome deletion syndrome. 22q11.2 deletion may result in variable clinical phenotypes which may differ even between patients with identical deletions. Abnormal pharyngeal arch development results in defects in the development of the parathyroid glands, thymus and conotruncal region of the heart. Defective thymic development is associated with impaired immune function. 'Complete' DiGeorge syndrome with total absence of the thymus and a severe T-cell immunodeficiency accounts for <0.5% of patients. The majority of patients with 22q11.2 deletion syndromes have 'partial' defects with impaired thymic development rather than complete absence with variable defects in T-cell numbers. Immunodeficiency in these patients is not solely due to T-cell deficiency and abnormalities of T-cell clonality or impairment of proliferative responses may play a role. Humoral deficiencies including defects in the B-cell compartment have also been identified in these patients. 22q11.2 deletion syndrome patients are at increased risk of a variety of autoimmune diseases. A number of immune defects may predispose to the development of autoimmunity in these patients including increased infection, impaired development of natural T-regulatory cells and impaired thymic central tolerance.

Review of 54 patients with complete DiGeorge anomaly enrolled in protocols for thymus transplantation: outcome of 44 consecutive transplants

The purpose of this study was to characterize a large group of infants with complete DiGeorge anomaly and to evaluate the ability of thymus transplantation to reconstitute immune function in these infants. DiGeorge anomaly is characterized by varying defects of the heart, thymus, and parathyroid glands. Complete DiGeorge anomaly refers to the subgroup that is athymic (< 1%). The characteristics of 54 subjects at presentation and results from 44 consecutive thymus transplantations are reported. Remarkably, only 52% had 22q11 hemizygosity and only 57% had congenital heart disease requiring surgery. Thirty-one percent developed an atypical phenotype with rash and lymphadenopathy. To date, 33 of 44 subjects who received a transplant survive (75%) with post-transplantation follow-up as long as 13 years. All deaths occurred within 12 months of transplantation. All 25 subjects who were tested 1 year after transplantation had developed polyclonal T-cell repertoires and proliferative responses to mitogens. Adverse events developing after transplantation included hypothyroidism in 5 subjects and enteritis in 1 subject. In summary, diagnosis of complete DiGeorge anomaly is challenging because of the variability of presentation. Thymus transplantation was well tolerated and resulted in stable immunoreconstitution in these infants.

Inflammatory responses in the placenta and umbilical cord

Histopathological examination of the placenta is the gold standard for evaluating antenatal inflammatory processes that might influence fetal development. Histological chorioamnionitis develops through a well-characterised stereotyped progression of maternal and fetal cellular stages that vary from patient to patient and are amenable to quantification. Increases in the intensity of these responses and their gradual transformation into a chronic phase are important variables that can adversely affect fetal physiology. Under recognised placental inflammatory lesions affecting the decidua, placental villi and fetal vessels are also potentially informative factors that should be taken into account in the studies of adverse pregnancy outcomes. This review summarises the relationships between aetiology, intensity, duration, characteristics and site of histological placental inflammation and suggests how these data may help to better understand the antenatal environment.

Maternal microchimerism in the livers of patients with biliary atresia

Background

Biliary atresia (BA) is a neonatal cholestatic disease of unknown etiology. It is the leading cause of liver transplantation in children. Many similarities exist between BA and graft versus host disease suggesting engraftment of maternal cells during gestation could result in immune responses that lead to BA. The aim of this study was to determine the presence and extent of maternal microchimerism (MM) in the livers of infants with BA.

Methods

Using fluorescent in situ hybridization (FISH), 11 male BA & 4 male neonatal hepatitis (NH) livers, which served as controls, were analyzed for X and Y-chromosomes. To further investigate MM in BA, 3 patients with BA, and their mothers, were HLA typed. Using immunohistochemical stains, the BA livers were examined for MM. Four additional BA livers underwent analysis by polymerase chain reaction (PCR) for evidence of MM.

Results

By FISH, 8 BA and 2 NH livers were interpretable. Seven of eight BA specimens showed evidence of MM. The number of maternal cells ranged from 2–4 maternal cells per biopsy slide. Neither NH specimen showed evidence of MM. In addition, immunohistochemical stains confirmed evidence of MM. Using PCR, a range of 1–142 copies of maternal DNA per 25,000 copies of patients DNA was found.

Conclusions

Maternal microchimerism is present in the livers of patients with BA and may contribute to the pathogenesis of BA.

Complete DiGeorge syndrome: Development of rash, lymphadenopathy, and oligoclonal T cells in 5 cases

BACKGROUND

Five patients with DiGeorge syndrome presented with infections, skin rashes, and lymphadenopathy after the newborn period. T-cell counts and function varied greatly in each patient. Initial laboratory testing did not suggest athymia in these patients.

OBJECTIVE

The purpose of this study was to determine whether the patients had significant immunodeficiency.

METHODS

Research testing of peripheral blood included immunoscope evaluation of T-cell receptor beta variable gene segment repertoire diversity, quantification of T-cell receptor rearrangement excision circles, and detection of naive T cells (expressing CD45RA and CD62L).

RESULTS

The patients were classified as having DiGeorge syndrome on the basis of syndromic associations and heart, parathyroid, and immune abnormalities. Immunoscope evaluation revealed that the T-cell repertoires were strikingly oligoclonal in all patients. There were few recent thymic emigrants, as indicated by the very low numbers of naive T cells (<50/mm(3)) and the absence of T-cell receptor rearrangement excision circles. These studies showed that all 5 patients were athymic. Two patients died, one from infection. No thymus was found during the complete autopsy performed on one patient.

CONCLUSION

Patients with DiGeorge syndrome, skin rash, and lymphadenopathy should undergo analysis of naive T-cell numbers and of T-cell receptor beta variability segment repertoire to determine whether they are athymic, even if they have T cells with mitogen responsiveness. It is important for physicians to realize that patients with complete DiGeorge syndrome remain profoundly immunodeficient after development of these atypical features (rash, lymphadenopathy, and oligoclonal T cells). Prompt diagnosis is necessary for appropriate management.

Impaired thymic output and restricted T-cell repertoire in two infants with immunodeficiency and early-onset generalized dermatitis

We evaluated the T-cell repertoire and the thymic output in two infants, one with Omenn Syndrome (OS) and another with complete DiGeorge Syndrome (DGS), who developed generalized dermatitis. The patients shared common T-cell abnormalities, as demonstrated by the low response to mitogenic stimulation, by an unusual usage of specific T-cell receptor (TCR) segments, and by a reduction of TCR diversity in both alpha/beta and gamma/delta populations. Furthermore, they both showed an impaired thymic function, as assessed by the low number of TCR recombination excision circles, which are formed from excised DNA during the rearrangement of TCR genes. These data indicated that generalized erythrodermia may be present in different forms of T-cell immunodeficiency and may reflect intrinsic defects in either V(D)J recombination or in thymic development, leading to the peripheral expansion of T-cell clonotypes, that bear peculiar TCR chains.