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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. (Blood. 2007; 109: [4539][4540][4541][4542][4543][4544][4545][4546][4547]

FOXN1 deficiency is a primary immunodeficiency characterized by athymia, alopecia totalis, and nail dystrophy. Two infants with FOXN1 deficiency were transplanted with cultured postnatal thymus tissue. Subject 1 presented with disseminated Bacillus Calmette-Guérin infection and oligoclonal T cells with no naive markers. Subject 2 had respiratory failure, human herpes virus 6 infection, cytopenias, and no circulating T cells. The subjects were given thymus transplants at 14 and 9 months of life, respectively. Subject 1 received immunosuppression before and for 10 months after transplantation. With follow up of 4.9 and 2.9 years, subjects 1 and 2 are well without infectious complications. The pretransplantation mycobacterial disease in subject 1 and cytopenias in subject 2 resolved. Subject 2 developed autoimmune thyroid disease 1.6 years after transplantation. Both subjects developed functional immunity. Subjects 1 and 2 have 1053/mm3 and 1232/mm3 CD3+ cells, 647/mm3 and 868/mm3 CD4+ T cells, 213/mm3 and 425/mm3 naive CD4+ T cells, and 10 200 and 5700 T-cell receptor rearrangement excision circles per 100 000 CD3+ cells, respectively. They have normal CD4 T-cell receptor β variable repertoires. Both subjects developed antigen-specific proliferative responses and have discon-tinued immunoglobulin replacement. In summary, thymus transplantation led to T-cell reconstitution and function in these FOXN1 deficient infants.

BackgroundThymus transplantation is a promising strategy for the treatment of athymic complete DiGeorge syndrome (cDGS).MethodsTwelve patients with cDGS underwent transplantation with allogeneic cultured thymus.ObjectiveWe sought to confirm and extend the results previously obtained in a single center.ResultsTwo patients died of pre-existing viral infections without having thymopoiesis, and 1 late death occurred from autoimmune thrombocytopenia. One infant had septic shock shortly after transplantation, resulting in graft loss and the need for a second transplant. Evidence of thymopoiesis developed from 5 to 6 months after transplantation in 10 patients. Median circulating naive CD4 counts were 44 × 106/L (range, 11-440 × 106/L) and 200 × 106/L (range, 5-310 × 106/L) at 12 and 24 months after transplantation and T-cell receptor excision circles were 2,238/106 T cells (range, 320-8,807/106 T cells) and 4,184/106 T cells (range, 1,582-24,596/106 T cells). Counts did not usually reach normal levels for age, but patients were able to clear pre-existing infections and those acquired later. At a median of 49 months (range, 22-80 months), 8 have ceased prophylactic antimicrobials, and 5 have ceased immunoglobulin replacement. Histologic confirmation of thymopoiesis was seen in 7 of 11 patients undergoing biopsy of transplanted tissue, including 5 showing full maturation through to the terminal stage of Hassall body formation. Autoimmune regulator expression was also demonstrated. Autoimmune complications were seen in 7 of 12 patients. In 2 patients early transient autoimmune hemolysis settled after treatment and did not recur. The other 5 experienced ongoing autoimmune problems, including thyroiditis (3), hemolysis (1), thrombocytopenia (4), and neutropenia (1).ConclusionsThis study confirms the previous reports that thymus transplantation can reconstitute T cells in patients with cDGS but with frequent autoimmune complications in survivors.

Thymus transplantation is a promising investigational therapy for infants born with no thymus. Because of the athymia, these infants lack of T cell development and have a severe primary immunodeficiency. Although thymic hypoplasia or aplasia is characteristic of DiGeorge anomaly, in “complete” DiGeorge anomaly, there is no detectable thymus as determined by the absence of naïve (CD45RA+, CD62L+) T cells. Transplantation of postnatal allogeneic cultured thymus tissue was performed in sixty subjects with complete DiGeorge anomaly who were under the age of 2 years. Recipient survival was over 70%. Naïve T cells developed 3–5 months after transplantation. The graft recipients were able to discontinue antibiotic prophylaxis, and immunoglobulin replacement. Immunosuppression was used in a subset of subjects but was discontinued when naïve T cells developed. The adverse events have been acceptable with thyroid disease being the most common. Research continues on mechanisms underlying immune reconstitution after thymus transplantation.

A regulatory element upstream of the human myoglobin gene functions as a muscle-specific enhancer (MSE) in conjunction with core promoter elements of the myoglobin gene, but not in combination with the simian virus 40 (SV40) early promoter. These two promoters differ in the sequences of their 'TATA boxes': for the myoglobin gene, the sequence is TATAAAA, whereas for SV40, the sequence is TATTTAT. We have now tested the hypothesis that this sequence difference is responsible for the differential response of the promoters to the MSE. We found that when the TATA box sequence of the myoglobin promoter was changed to that of the SV40 promoter, responsiveness to the MSE was abolished; conversely, when the SV40 TATA box sequence was changed to that of the myoglobin promoter, the promoter became responsive to the MSE. We conclude that mammalian TATA-box elements are functionally heterogeneous, and suggest that this heterogeneity reflects differential interactions with distinctive TATA box-binding factors, only some of which can act cooperatively with MSE-binding proteins to generate an active transcriptional complex.

Complete DiGeorge syndrome is a fatal congenital disorder characterized by athymia, hypoparathyroidism, and heart defects. Less than half of patients are 22q11 hemizygous. The goal of this study was to assess if immune suppression followed by postnatal thymus transplantation would lead to T-cell function in 6 infant patients who had host T cells at the time of transplantation. All infants had fewer than 50 recent thymic emigrants (CD3 ؉ CD45RA IntroductionDiGeorge syndrome is a congenital disorder characterized by defects in the third and fourth pharyngeal pouches, although abnormalities can be found extending from the first through sixth pharyngeal arches. 1 Typically, defects are found in the heart, parathyroid gland, and thymus. [2][3][4][5][6] The immune defect in DiGeorge syndrome usually is mild. In fewer than 1% of cases, there is profound immune deficiency secondary to athymia. 7 Athymic patients are categorized as having complete DiGeorge syndrome. 2,8 Patients with complete DiGeorge syndrome usually die within the first 2 years of life. 2 Severe recurrent infections are a major problem. 2 Peripheral blood testing can be used to identify those patients with DiGeorge syndrome who are athymic. Naive T cells (recent thymic emigrants) coexpress CD45RA and CD62L. 9 We define athymic patients as those having less than 50 naive T cells/cubic millimeter (mm 3 ). 10 In patients having a sufficient blood volume for testing, we also quantitate the number of T-cell receptor rearrangement excision circles (TRECs) in circulating T cells. [11][12][13] TRECs are episomal DNA circles that form when T-cell receptor (TCR) gene segments rearrange in the thymus. Athymic patients have less than 100 TRECs/100 000 T cells (normal value for a newborn is approximately 10 000 TRECs/100 000 T cells). 10 Most athymic patients with DiGeorge syndrome have very low proliferative responses to mitogens and very low T-cell numbers. These patients can be treated with postnatal allogeneic thymus transplantation without immunosuppression. 10 The mechanism of this experimental treatment is the migration of host bone marrow cells to slices of cultured donor thymus that are implanted into the patient's muscle. In the donor graft, the host bone marrow cells develop via thymopoiesis into host T cells that then emigrate out of the thymus into the peripheral blood.We report the results of postnatal allogeneic thymus transplantation in 6 athymic patients with DiGeorge syndrome who had some T cells and T-cell proliferative responses to mitogens. Because of their T-cell function, these patients would likely have rejected allotransplants if no immunosuppression had been given. Thus, all patients were initially treated with Thymoglobulin (rabbit antithymocyte globulin, Imtix-SangStat, Lyon, France). This treatment was immediately followed by postnatal cultured allogeneic thymus transplantation. The excellent clinical and immunologic results in this group of patients supports the use of Thymoglobulin together with thymus transplantation to effect normal...

Complete DiGeorge anomaly is characterized by athymia, congenital heart disease and hypoparathyroidism. This congenital disease is fatal by age 2 years unless immune reconstitution is successful. There are multiple underlying syndromes associated with complete DiGeorge anomaly including 22q11 hemizygosity in approximately 50%, CHARGE association in approximately 25%, and diabetic embryopathy in approximately 15%. Approximately one third of patients present with rash and lymphadenopathy associated with oligoclonal “host” T cells. This condition resembles Omenn syndrome. Immunosuppression is necessary to control the oligoclonal T cells. The results of thymus transplantation are reported for a series of 50 patients, 36 of whom survive. The survivors develop naïve T cells and a diverse T cell repertoire.