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We report the clinical description and molecular dissection of a new fatal human inherited disorder characterized by chronic autoinflammation, invasive bacterial infections and muscular amylopectinosis. Patients from two kindreds carried biallelic loss-of-expression and loss-of-function mutations in HOIL1 (RBCK1), a component of the linear ubiquitination chain assembly complex (LUBAC). These mutations resulted in impairment of LUBAC stability. NF-κB activation in response to interleukin 1β (IL-1β) was compromised in the patients' fibroblasts. By contrast, the patients' mononuclear leukocytes, particularly monocytes, were hyper-responsive to IL-1β. The consequences of human HOIL-1 and LUBAC deficiencies for IL-1β responses thus differed between cell types, consistent with the unique association of autoinflammation and immunodeficiency in these patients. These data suggest that LUBAC regulates NF-κB-dependent IL-1β responses differently in different cell types.

In this retrospective collaborative study, we have analyzed long-term outcome and donor cell engraftment in 194 patients with Wiskott-Aldrich syndrome (WAS) who have been treated by hematopoietic cell transplantation (HCT) in the period 1980- 2009. Overall survival was 84.0% and was even higher (89.1% 5-year survival) for those who received HCT since the year 2000, reflecting recent improvement of outcome after transplantation from mismatched family donors and for patients who received HCT from an unrelated donor at older than 5 years. Patients who went to transplantation in better clinical conditions had a lower rate of post-HCT complications. Retrospective analysis of lineage-specific donor cell engraftment showed that stable full donor chimerism was attained by 72.3% of the patients who survived for at least 1 year after HCT. Mixed chimerism was associated with an increased risk of incomplete reconstitution of lymphocyte count and post-HCT autoimmunity, and myeloid donor cell chimerism < 50% was associated with persistent thrombocytopenia. These observations indicate continuous improvement of outcome after HCT for WAS and may have important implications for the development of novel protocols aiming to obtain full correction of the disease and reduce post-HCT complications.

Background: Hematopoietic stem cell transplantation remains the only treatment for most patients with severe combined immunodeficiencies (SCIDs) or other primary immunodeficiencies (non-SCID PIDs)., Objective: To analyze the long-term outcome of patients with SCID and non-SCID PID from European centers treated between 1968 and 2005., Methods: The product-limit method estimated cumulative survival; the log-rank test compared survival between groups. A Cox proportional-hazard model evaluated the impact of independent predictors on patient survival., Results: In patients with SCID, survival with genoidentical donors (n = 25) from 2000 to 2005 was 90%. Survival using a mismatched relative (n = 96) has improved (66%), similar to that using an unrelated donor (n = 46; 69%; P = .005). Transplantation after year 1995, a younger age, B(+) phenotype, genoidentical and phenoidentical donors, absence of respiratory impairment, or viral infection before transplantation were associated with better prognosis on multivariate analysis. For non-SCID PID, in contrast with patients with SCID, we confirm that, in the 2000 to 2005 period, using an unrelated donor (n = 124) gave a 3-year survival rate similar to a genoidentical donor (n = 73), 79% for both. Survival was 76% in phenoidentical transplants (n = 23) and worse in mismatched related donor transplants (n = 47; 46%; P = .016)., Conclusion: This is the largest cohort study of such patients with the longest follow-up. Specific issues arise for different patient groups. Patients with B-SCID have worse survival than other patients with SCID, despite improvements in each group. For non-SCID PID, survival is worse than SCID, although more conditions are now treated. Individual disease categories now need to be analyzed so that disease-specific prognosis may be better understood and the best treatments planned., (Copyright (c) 2010 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.)

Cartilage-hair hypoplasia (CHH) is a rare autosomal recessive disease caused by mutations in the RMRP gene. Beside dwarfism, CHH has a wide spectrum of clinical manifestations including variable grades of combined immunodeficiency, autoimmune complications, and malignancies. Previous reports in single CHH patients with significant immunodeficiencies have demonstrated that allogeneic hematopoietic stem cell transplantation (HSCT) is an effective treatment for the severe immunodeficiency, while growth failure remains unaffected. Because long-term experience in larger cohorts of CHH patients after HSCT is currently unreported, we performed a European collaborative survey reporting on 16 patients with CHH and immunodeficiency who underwent HSCT. Immune dysregulation, lymphoid malignancy, and autoimmunity were important features in this cohort. Thirteen patients were transplanted in early childhood ( approximately 2.5 years). The other 3 patients were transplanted at adolescent age. Of 16 patients, 10 (62.5%) were long-term survivors, with a median follow-up of 7 years. T-lymphocyte numbers and function have normalized, and autoimmunity has resolved in all survivors. HSCT should be considered in CHH patients with severe immunodeficiency/autoimmunity, before the development of severe infections, major organ damage, or malignancy might jeopardize the outcome of HSCT and the quality of life in these patients.

Infantile malignant osteopetrosis (IMO) includes various genetic disorders that affect osteoclast development and/or function. Genotype-phenotype correlation studies in IMO have been hampered by the rarity and heterogeneity of the disease and by the severity of the clinical course, which often leads to death early in life. We report on the clinical and molecular findings and treatment in 20 consecutive patients (11 males, nine females) with IMO, diagnosed at a single center in the period 1991-2008. Mean age at diagnosis was 3.9 months, and mean follow-up was 66.75 months. Mutations in TCIRG1, OSTM1, ClCN7, and TNFRSF11A genes were detected in nine, three, one, and one patients, respectively. Six patients remain genetically undefined. OSTM1 and ClCN7 mutations were associated with poor neurologic outcome. Among nine patients with TCIRG1 defects, six presented with hypogammaglobulinemia, and one showed primary pulmonary hypertension. Fourteen patients received hematopoietic cell transplantation; of these, nine are alive and eight of them have evidence of osteoclast function. These data may provide a basis for informed decisions regarding the care of patients with IMO.

We review clinical outcome and immune reconstitution in a consecutive series of 74 infants with severe T cell immunodeficiency who received hematopoietic cell transplantation (HCT) from January 1991 to May 2003. Fifty-three patients (71.6%) are alive. Results were significantly better for recipients of HCT from HLA-matched related donors (100% survival) and unrelated donors (86.4%) than from mismatched related donors (51.6%). A detailed analysis of immune reconstitution and clinical status was performed in 49 surviving patients, most of which have attained robust T and B cell reconstitution and are in very good clinical conditions. No cases of late deaths or of chronic graft-versus-host disease (GvHD) have been observed. However, infections and autoimmunity at >1 year after HCT have been observed in a significant number of patients. Persistence of a low number of circulating naive T cells and long-term requirement for intravenous immunoglobulin were associated with a higher incidence of clinical events.

Background: Cartilage hair hypoplasia is an autosomal recessive type of metaphyseal chondrodysplasia, caused by mutations in the ribonuclease mitochondrial RNA processing (RMRP) gene. Typical features of cartilage hair hypoplasia include short stature, a predisposition to malignancy, and a variable degree of impairment of cellular immunity., Objective: We sought to describe the heterogeneity of clinical and immunologic phenotype in 12 consecutive patients with RMRP mutations who were referred to 2 different institutions for immunologic evaluation., Methods: We have retrospectively analyzed the clinical and laboratory features in 12 patients with molecular defects in the RMRP gene. T-cell repertoire was investigated by quantitating Vbeta families' expression and analyzing their diversity. T-cell receptor excision circle analysis was used to study thymic output., Results: All 12 patients had significant immune abnormalities, leading to severe immune deficiency in 9. CD8 lymphocytopenia was identified as a novel phenotype associated with RMRP mutations. Significant, even intrafamilial, phenotypic heterogeneity was observed. In 3 cases, severe immunodeficiency was the only phenotypic manifestation associated with RMRP mutations, a novel finding. Mutations leading to significant immune defects were most often located in the promoter, and the first case of a compound heterozygote for 2 such mutations is reported., Conclusion: This report broadens the spectrum of phenotypes associated with RMRP mutations and suggests that mutations in this gene should be considered when evaluating patients with combined immune deficiency, regardless of the presence of other manifestations.

Autosomal-Recessive Osteopetrosis (ARO) comprises a heterogeneous group of bone diseases for which mutations in five genes are known as causative. Most ARO are classified as osteoclast-rich, but recently a subset of osteoclast-poor ARO has been recognized as due to a defect in TNFSF11 (also called RANKL or TRANCE, coding for the RANKL protein), a master gene driving osteoclast differentiation along the RANKL-RANK axis. RANKL and RANK (coded for by the TNFRSF11A gene) also play a role in the immune system, which raises the possibility that defects in this pathway might cause osteopetrosis with immunodeficiency. From a large series of ARO patients we selected a Turkish consanguineous family with two siblings affected by ARO and hypogammaglobulinemia with no defects in known osteopetrosis genes. Sequencing of genes involved in the RANKL downstream pathway identified a homozygous mutation in the TNFRSF11A gene in both siblings. Their monocytes failed to differentiate in vitro into osteoclasts upon exposure to M-CSF and RANKL, in keeping with an osteoclast-intrinsic defect. Immunological analysis showed that their hypogammaglobulinemia was associated with impairment in immunoglobulin-secreting B cells. Investigation of other patients revealed a defect in both TNFRSF11A alleles in six additional, unrelated families. Our results indicate that TNFRSF11A mutations can cause a clinical condition in which severe ARO is associated with an immunoglobulin-production defect.

Wiskott-Aldrich syndrome (WAS) is a rare X-linked immunodeficiency with microthrombocytopenia, eczema, recurrent infections, autoimmune disorders, and malignancies that are life-threatening in the majority of patients. In this long-term, retrospective, multicenter study, we analyzed events that occurred in 96 WAS patients who received transplants between 1979 and 2001 who survived at least 2 years following hematopoietic stem-cell transplantation (HSCT). Events included chronic graft-versus-host disease (cGVHD), autoimmunity, infections, and sequelae of before or after HSCT complications. Three patients (3%) died 2.1 to 21 years following HSCT. Overall 7-year event-free survival rate was 75%. It was lower in recipients of mismatched related donors, also in relation with an older age at HSCT and disease severity. The most striking finding was the observation of cGVHD-independent autoimmunity in 20% of patients strongly associated with a mixed/split chimerism status (P < .001), suggesting that residual-host lymphocytes can mediate autoimmune disease despite the coexistence of donor lymphocytes. Infectious complications (6%) related to splenectomy were also significant and may warrant a more restrictive approach to performing splenectomy in WAS patients. Overall, this study provides the basis for a prospective, standardized, and more in-depth detailed analysis of chimerism and events in long-term follow-up of WAS patients who receive transplants to design better-adapted therapeutic strategies.

Hypomorphic mutations of the RAG genes in humans are associated with a spectrum of clinical and immunologic presentations that range from T(-) B(-) severe combined immune deficiency (SCID) to Omenn syndrome. In most cases, residual V(D)J recombination activity allows for development of few T-cell clones, which expand in the periphery and infiltrate target organs, resulting in tissue damage. Invariant natural killer T (iNKT) cells play an important immunoregulatory role and have been associated with protection against autoimmunity. We now report on 5 unrelated cases of combined immune deficiency due to hypomorphic RAG mutations, and demonstrate the absence of iNKT cells in all 5 patients. These findings suggest that lack of this important immunoregulatory cell population may contribute to the pathophysiology of Omenn syndrome.

Background: Currently, hematopoietic stem cell transplantation allows long-term survival in a high proportion of infants with congenital severe T-cell immunodeficiency. However, relatively little is known of their long-term quality of life., Objective: We sought to assess the long-term immune reconstitution and clinical status in children treated with stem cell transplantation for severe T-cell immunodeficiency., Methods: Immune function and clinical status have been analyzed in a cohort of 40 patients with severe T-cell immunodeficiency who are alive at a follow-up of at least 5 years after transplantation., Results: Most patients have attained normal T- and B-cell function. Weight and height were normal at last follow-up in most patients. Endocrine and severe neurologic abnormalities have been observed in 17.5% and 10% of the patients, respectively., Conclusions: These data indicate that with current management strategies, stem cell transplantation can lead to long-term survival and good quality of life in the majority of patients with severe T-cell immunodeficiency., Clinical Implications: Prompt recognition of congenital severe T-cell immunodeficiency, followed by stem cell transplantation, allows excellent perspectives of long-term survival and good quality of life for these otherwise fatal disorders.

Development of patient-tailored prognostic and therapeutic strategies remains a major, yet largely unmet, goal of medicine. Studies performed in patients who carry mutations in the Wiskott-Aldrich syndrome protein (WASP) gene have indicated the feasibility, but also the limitations, of this approach. In this review, we discuss the importance of specific WASP mutations, and their effects on protein expression and function in determining the spectrum of clinical phenotypes associated with WASP defects. The array of currently available and foreseeable therapeutic options is reviewed in this context as a model for other more common genetic disorders.

Primary immune deficiencies (PID) comprise a heterogeneous group of genetically determined disorders that affect development and/or function of innate or adaptive immunity. Consequently, patients with PID suffer from recurrent and/or severe infections that frequently involve the lung. While the nature of the immune defect often dictates the type of pathogens that may cause lung infection, there is substantial overlap of radiological findings, so that appropriate laboratory tests are mandatory to define the nature of the immune defect and to prompt appropriate treatment. At the same time, the recent identification of a large number of PID-causing genes now allows early, even presymptomatic diagnosis, thus representing an essential tool for prevention of lung damage. This review article describes the most common forms of PID, their cellular and molecular bases, and the associated lung abnormalities, and reports on available treatment., ((c) 2007 S. Karger AG, Basel.)

Context: Bone marrow transplantation (BMT) using stem cells obtained from a family-related, HLA-identical donor (RID) is the optimal treatment for patients with severe combined immune deficiency (SCID). In the absence of an RID, HLA-mismatched related donors (MMRDs) are often used. However, compared with RIDs, use of MMRDs for BMT is associated with reduced survival and inferior long-term immune reconstitution. Use of HLA-matched unrelated donors (MUDs) represents another potential alternative for BMT., Objective: To compare outcomes and immune reconstitution in a large cohort of patients with SCID who received RID, MUD, or MMRD BMT., Design, Setting, and Patients: Retrospective study of medical records from 94 infants diagnosed as having SCID who received BMT between 1990 and 2004 at 1 Canadian and 1 Italian pediatric referral center. Thirteen, 41, and 40 patients received RID, MUD, and MMRD BMT, respectively., Main Outcome Measures: Survival and graft failure, along with incidence of graft-vs-host disease, infections, and other complications; immune reconstitution was assessed in children who survived for more than 2 years after BMT., Results: Survival after RID BMT was highest. Twelve (92.3%) of 13 patients who received RID BMT, 33 (80.5%) of 41 who received MUD BMT, and 21 (52.5%) of 40 patients who received MMRD BMT survived. Compared with MMRD BMT, survival was significantly higher with RID (P = .008) or with MUD (P = .03). Graft failures and need for repeat BMT were more common in patients receiving MMRD BMT than in those who underwent MUD BMT. Long-term reconstitution of a full T-cell repertoire was achieved more frequently following MUD BMT (94.7%) than after MMRD BMT (61.1%) (P = .02). Acute graft-vs-host disease was documented in 73.1% of patients following MUD BMT but in only 45% after MMRD BMT (P = .009). Conversely, interstitial pneumonitis was observed more frequently after MMRD BMT (14 [35.0%] of 40) than after MUD BMT (3 [7.3%] of 41; P = .002)., Conclusion: Our study suggests that in the absence of a relative with identical HLA, MUD BMT may provide better engraftment, immune reconstitution, and survival for patients with SCID than MMRD BMT.

Analysis of gene-targeted mice and patients with severe combined immunodeficiency due to mutations of the alpha chain of the interleukin-7 receptor (IL-7Ralpha) has shown important differences between mice and humans in the role played by IL-7 in lymphoid development. More recently, it has been shown that IL-7Ralpha is also shared by the receptor for another cytokine, thymic stromal lymphopoietin (TSLP). In this review, we discuss recent advances in IL-7- and TSLP-mediated signaling. We also report on the clinical and immunological features of 16 novel patients with IL-7Ralpha deficiency and discuss the results of hematopoietic stem cell transplantation.

Purpose of Review: To review the clinical and molecular features of autoimmune polyendocrinopathy candidiasis and ectodermal dystrophy and discuss recent advances in the function of the AIRE protein. We will summarize how AIRE contributes to immunological tolerance, and thus to the prevention of autoimmunity., Recent Findings: The organization of a well-structured thymic microenvironment and the interaction between nascent thymocytes and thymic epithelial cells have been shown to be essential for AIRE expression. AIRE is involved in the expression of ectopic proteins by medullary thymic epithelial cells. This allows the establishment of central tolerance and contributes to the prevention of organ-specific autoimmunity, as shown by findings in patients with autoimmune polyendocrinopathy candidiasis and ectodermal dystrophy (a disease caused by AIRE gene mutations) and in aire (-/-) mice., Summary: Autoimmune polyendocrinopathy candidiasis and ectodermal dystrophy represents a unique model to investigate the cellular and molecular mechanisms that govern central tolerance and help prevent autoimmunity. Recent findings indicate that the compartmentalization of AIRE and interaction with other proteins are involved in this mechanism. The disturbance of AIRE expression may also be responsible for autoimmune manifestations in disorders with disrupted thymic structure other than autoimmune polyendocrinopathy candidiasis and ectodermal dystrophy alone.

The chemokine receptor CXCR4 and its functional ligand, CXCL12, are essential regulators of development and homeostasis of hematopoietic and lymphoid organs. Heterozygous truncating mutations in the CXCR4 intracellular tail cause a rare genetic disease known as WHIM syndrome (warts, hypogammaglobulinemia, infections, myelokathexis), whose pathophysiology remains unclear. We report CXCR4 function in 3 patients with WHIM syndrome carrying heterozygous truncating mutations of CXCR4. We show that CXCR4 gene mutations in WHIM patients do not affect cell surface expression of the chemokine receptor and its internalization upon stimulation with CXCL12. Moreover, no significant differences in calcium mobilization in response to CXCL12 are found. However, the chemotactic response of both polymorphonuclear cells and T lymphocytes in response to CXCL12 is increased. Furthermore, immunophenotypic analysis of circulating T and B lymphocytes reveals a decreased number of memory B cells and of naive T cells and an accumulation of effector memory T cells associated with a restricted T-cell repertoire. Based on our results, we suggest that the altered leukocyte response to CXCL12 may account for the pathologic retention of mature polymorphonuclear cells in the bone marrow (myelokathexis) and for an altered lymphocyte trafficking, which may cause the immunophenotyping abnormalities observed in WHIM patients.

Background and Objectives: In utero transplantation of hematopoietic stem cells allows immune reconstitution of fetuses with severe combined immunodeficiency. The objective of this work was to study the quality of T-cell reconstitution following this procedure., Design and Methods: We evaluated the kinetics and extent of T-cell reconstitution in five infants with severe combined immune deficiency (SCID), three with a B+ and two with a B- phenotype, who received haploidentical stem cell transplantation before birth. To this end, we measured the frequency of T-cell receptor excision circles (TREC) and the diversity of the T-cell repertoire., Results: In utero transplantation led to engraftment of donor-derived T lymphocytes which attained normal numbers in four infants, who are in good health. In the three patients with a B+ phenotype, generation of a heterogeneous T-cell repertoire was associated with development of TREC levels comparable to those of SCID patients treated by post-natal transplantation and of healthy babies. Of the two patients with a B- phenotype, one developed mixed T-cell chimerism and a substantial number of circulating T cells, associated with a variable heterogeneity of the T-cell repertoire; TREC levels were normal soon after birth, but declined thereafter. The remaining B- patient remained lymphopenic with a skewed T-cell repertoire and very low TREC levels. This patient eventually required transplantation from a matched unrelated donor at 5 years of age, but died of EBV-related lymphoproliferative disease., Interpretation and Conclusions: These data indicate that in utero transplantation of fetuses with B+ SCID allows generation of newly diversified T lymphocytes and ensures long-term reconstitution of cell-mediated immunity.

CD40 ligand (CD40L) deficiency causes recurrent sinopulmonary infection, Pneumocystis carinii pneumonia, and Cryptosporidium parvum infection. Approximately 40% to 50% of patients survive to the third decade: long-term survival is unclear. Hematopoietic stem cell transplantation (HSCT) is curative. We present a retrospective analysis of 38 European patients undergoing HSCT for CD40L deficiency in 8 European countries between 1993 and 2002. Donor stem cell source included 14 HLA-identical siblings, 22 unrelated donors, and 2 phenotypically matched parental stem cells (12 T-cell depleted). Of the patients, 34 engrafted and 26 (68%) survived; 3 had autologous reconstitution, 22 (58%) were cured, and 1 engrafted but has poor T-cell immune reconstitution. There were 18 evaluated patients who responded to vaccination. Of the patients, 12 (32%) died from infection-related complications, with severe cryptosporidiosis in 6. Grades 2 to 4 graft-versus-host disease (GvHD) associated with infection occurred in 6 of 12 fatal cases. HSCT cured 58% of patients, 72% of those without hepatic disease. Early T-cell function following whole marrow HSCT may limit cryptosporidial disease, but survival was similar after T-cell-depleted HSCT. Preexisting lung damage was the most important adverse risk factor. Further studies will determine optimal timing and type of HSCT.

Primary immune deficiencies (PID) represent inborn errors of immunity. Over the years, detailed analysis of the clinical and laboratory features associated with these unique and rare disorders have shed light on the complex array of signals and processes that govern development and activation of the immune system. While the first examples of PID pertained to severe defects in lymphoid development, more recently a variety of gene defects have been identified in humans that do not compromize the ability to generate lymphocytes, but rather result in profound immune dysregulation. In many cases, identification of the molecular and cellular bases of PID has preceeded development of animal models by gene targeting. Finally, since the very first cases reported in humans, PID have also represented a unique tool to investigate the efficacy of novel therapeutic approaches (from molecular therapy to hematopoietic stem cell transplantation to somatic cells gene therapy), that have been applied or may apply to a variety of more common human diseases.

Background and Objectives: Unrelated donor bone marrow transplant (UD-BMT) has become an attractive, alternative source of hematopoietic cells for patients lacking a matched sibling. The aim of this paper is to report on 520 patients below 19 years of age undergoing UD BMT in 31 Italian centers between September 1989 and December 2001, and to focus on the results achieved in the 423 patients grafted before December 2000., Designs and Methods: In 1989 the Italian Bone Marrow Transplant Group (GITMO) and the Italian Association for Pediatric Hematology and Oncology (AIEOP) established the Italian Bone Marrow Donor Registry (IBMDR) to facilitate donor search and marrow procurement for patients lacking an HLA identical sibling. By the end of December 2001, 296,720 HLA-A, B typed volunteer donors had been cumulatively registered and 3,411 searches had been activated for Italian patients. At least one HLA-A, B, DRB1 matched donor was found for 54% of the patients and 520 UD BMTs were performed in patients below 19 years of age before December 2001. Since 1999 more than 90% of the patients < or = 14 years old, and more than 50% of the patients 15-18 years old undergoing UD BMT have been treated in AIEOP institutions. In 50% of the cases donors were found in the IBMDR, and in 50% they were found in 14 other Registries. The average time from search activation to transplant was 6 months for diseases other than chronic myeloid leukemia (CML), while for CML it was 8.7 months., Results: Actuarial 100-day transplant-related mortality (TRM) was 32% in patients grafted between 1989 and 1997, and 21% for patients grafted after 1998 (p = 0.003). Twenty-eight per cent of the patients developed grade III or IV acute graft-versus-host disease (GvHD), and 20% developed extensive chronic GvHD. The rate of disease-free survival at three years was 37% for patients with acute lymphoblastic leukemia, 38% for acute myeloid leukemia or myelodysplastic syndrome patients, 59% for patients with inborn errors, and 51% for patients with CML., Interpretation and Conclusions: We conclude that the IBMDR has benefited a substantial number of patients lacking a matched sibling and has facilitated the recruitment of UDs into the international donor pool. Results show a positive trend after 1998, mainly due to a decrease in transplant-related-mortality.

Severe combined immunodeficiency (SCID) comprises a heterogeneous group of primary immunodeficiencies, a proportion of which are due to mutations in either of the 2 recombination activating genes (RAG)-1 and -2, which mediate the process of V(D)J recombination leading to the assembly of antigen receptor genes. It is reported here that the clinical and immunologic phenotypes of patients bearing mutations in RAGs are more diverse than previously thought and that this variability is related, in part, to the specific type of RAG mutation. By analyzing 44 such patients from 41 families, the following conclusions were reached: (1) null mutations on both alleles lead to the T-B-SCID phenotype; (2) patients manifesting classic Omenn syndrome (OS) have missense mutations on at least one allele and maintain partial V(D)J recombination activity, which accounts for the generation of residual, oligoclonal T-lymphocytes; (3) in a third group of patients, findings were only partially compatible with OS, and these patients, who also carried at least one missense mutation, may be considered to have atypical SCID/OS; (4) patients with engraftment of maternal T cells as a complication of a transplacental transfusion represented a fourth group, and these patients, who often presented with a clinical phenotype mimicking OS, may be observed regardless of the type of RAG gene mutation. Analysis of the RAG genes by direct sequencing is an effective way to provide accurate diagnosis of RAG-deficient as opposed to RAG-independent V(D)J recombination defects, a distinction that cannot be made based on clinical and immunologic phenotype alone.

Cytokines play a major role in lymphoid development. Defects of the common gamma chain (gamma(c)) or of the JAK3 protein in humans have been shown to result in a severe combined immune deficiency (SCID), with a profound defect in T and natural killer (NK)-cell development, whereas B-cell generation is apparently unaffected (T-B+NK-SCID). While extensive molecular and biochemical analysis of these patients has been instrumental in understanding better the biological properties of the gamma(c) and JAK3 protein, an unexpected phenotypic heterogeneity of gamma(c) and JAK3 deficiency has emerged, indicating the need for appropriate and extensive investigations even in patients with atypical presentations. At the same time, characterization of the defects has been instrumental in the development of novel therapeutic approaches, from in utero hematopoietic stem cell transplantation to gene therapy.

Bone marrow transplantation (BMT) is the treatment of choice in children affected by primary immunodeficiency (PID). Because only 10-15% of affected children have a familial HLA-identical donor alternative therapeutic options are BMT from a matched unrelated donor or an haploidentical BMT. In our experience only 40% of these children find a donor within the International Registry. Therefore, the remaining 50% children affected by PID are candidates for haploidentical BMT. Unfortunately, in PID other than sever-combined immunodeficiency (SCID), low engraftment rates have been reported because of minimal residual immunity. In order to enhance engraftment rate in haploidentical BMT in PID we suggest a protocol with addition of donor peripheral stem cells after mobilization with granulocyte colony-stimulating factor (G-CSF) (16 micrograms/kg for 5 days) and bone marrow cells. This procedure increases the cell load, which allows intensification of the conditioning regimen for induction of faster engraftment. The separation of CD34+ cells from leukapheresis products was achieved in the first 6 patients by the Isolex 300 system (Baxter) with a CD34+ cell purity range of 80-95% and in another three patients by the Clinimacs System (Miltenyi). The peripheral blood stem cells were cryopreserved until BMT, 15 days after G-CSF stimulation when the bone marrow was harvested, processed and T-cell depleted with Campath 1-M in the first 6 cases while the Clinimacs System was used in the remaining cases and no T-cell depletion was required. We included 9 patients in the study protocol: SCID (4), Omenn's syndrome (3), LAD (1) and CID (1). The mean value of peripheral CD34+ cells infused was 13.42 x 10(6)/kg and the mean CD3+ cells number was 0.385 x 10(5)/kg; the mean value of BM CD34+ cells infused was 10.62 x 10(6)/kg and the mean CD3+ cell number was 2.39 x 10(5)/kg. The mean number of infused CFU was 8.1 x 10(5)/kg for PBSC and 3.59 x 10(5)/kg for BM. The 9 patients achieved more than 0.5 x 10(9) peripheral blood neutrophils/L at a mean of 14.6 days (range: 6-22 days). One patient affected by SCID showed complete chimerism, but he died after BMT of systemic CMV infection; the other 8 patients are alive and well and 4 of them show complete chimerism in all cell lines. Split chimerism was documented in 2 SCID cases (CD3+ lymphocytes were of donor origin, monocytes were autologous and granulocytes were mainly autologous); 1 patient affected by Omenn's syndrome received 3 transplants (1 from the mother and 2 from the father, T-cells alone and bone marrow) and achieved engraftment with complete chimerism after the third transplant; the patient affected by LAD also received 3 transplants (2 bone marrow infusions and 1 PBSC infusion) achieving complete chimerism after the third one. In conclusion, the engraftment achieved in all treated patients, and the acceptable conditioning-related toxicity suggest that this approach could be successfully applied to children affected by PID and candidates for haploidentical BMT.

Combined immune deficiencies comprise a spectrum of genetic disorders characterized by developmental or functional defects of both T and B lymphocytes. Recent progress in cell biology and molecular genetics has unraveled the pathophysiology of most of these defects. In particular, the most common form of severe combined immune deficiency in humans, with lack of circulating T cells, a normal or increased number of B lymphocytes, and an X-linked pattern of inheritance (SCIDXI) has been shown to be due to defects of the IL2RG gene, encoding for the common gamma chain (gammac), shared by several cytokine receptors. Furthermore, defects of the JAK3 gene, encoding for an intracellular tyrosine kinase required for signal transduction through gammac-containing cytokine receptors, have been identified in patients with autosomal recessive T-B+ SCID. Characterization of the functional properties of cytokines that signal through the gammac-JAK3 signaling pathway has been favored by the detailed analysis of SCID patients. Specifically, the key role of IL-7 in promoting T cell development has been substantiated by the identification of rare patients with T-B+ SCID who have a defect in the alpha subunit of the IL-7 receptor (IL7Ralpha). The heterogeneity of genetic defects along the same signaling pathway that may lead to combined immune deficiency is paralleled by the heterogeneity of immunological phenotypes that may associate with defects in the same gene, thus creating a need for detailed immunological and molecular investigations in order to dissect the spectrum of combined immune deficiencies in humans.

We report on two patients affected with severe combined immune deficiency (SCID) with an unusual immunological phenotype and a substantial number of autologous, poorly functioning T cells. Distinct mutations identified at the IL2RG locus in the two patients impaired IL-2-mediated signaling but affected T-cell lymphopoiesis differently, resulting in generation of a polyclonal or oligoclonal T-cell repertoire. These observations add to the growing complexity of the immunological spectrum of SCID in humans and indicate the need for detailed immunological and molecular investigations in atypical cases.

Primary immunodeficiencies are inherited diseases characterized by impaired immune responses. In case of severe impairment of immunity bone marrow transplantation is the only therapeutic option. The molecular defect is known for several primary immunodeficiencies allowing prenatal diagnosis. This paper summarizes the clinical experience treating these pathologies by bone marrow transplantation.

Defects of the common gamma chain subunit of the cytokine receptors (gamma c) or of Jak3, a tyrosine kinase required for gamma c signal transduction, result in T-B+ severe combined immunodeficiency (SCID). However, atypical cases, characterized by progressive development of T lymphocytes, have been also reported. We describe a child with SCID caused by Jak3 gene defects, which strongly but not completely affect Jak3 protein expression and function, who developed a substantial number (> 3,000/microL) of autologous CD3+CD4+ T cells. These cells showed a primed/activated phenotype (CD45R0+ Fas+ HLA-DR+ CD62L(lo)), defective secretion of T-helper 1 and T-helper 2 cytokines, reduced proliferation to mitogens, and a high in vitro susceptibility to spontaneous (caused by downregulation of bcl-2 expression) as well as activation-induced cell death. A restricted T-cell receptor repertoire was observed, with oligoclonal expansion within each of the dominant segments. These features resemble those observed in gamma c-/y and in Jak3-/- mice, in which a population of activated, anergic T cells (predominantly CD4+) also develops with age. These results suggest that residual Jak3 expression and function or other Jak3-independent signals may also permit the generation of CD4+ T cells that undergo in vivo clonal expansion in humans; however, these mechanisms do not allow development of CD8+ T cells, nor do they fully restore the functional properties of CD4+ T lymphocytes.

Background: X-linked severe combined immunodeficiency (SCIDXI) is an inherited immune defect which leads to death in infancy from severe infections. The defect is caused by mutations of the IL-2RG gene that encodes for the common gamma chain shared by several cytokine receptors. The disease is characterised by lack of T and NK cells with normal numbers of B cells. SCIDXI can be cured by bone marrow transplantation (BMT) or prevented by abortion after prenatal diagnosis., Methods: A male fetus was diagnosed as having SCIDXI by molecular, immunophenotypic, and functional analyses. The fetus was injected intraperitoneally under ultrasound guidance with CD34 haematopoietic progenitor cells purified from paternal bone marrow and T-cell depleted by E rosetting. Chimerism analysis was by HLA-DQ alpha typing and gamma-chain staining on cord blood., Findings: A healthy 3.6 kg boy was delivered by caesarean section at 38 weeks of gestation with no clinical or laboratory signs of graft-versus-host disease. Engraftment of donor-derived CD2 cells was found at birth. At 3.5 months of age the infant is well and his T-cell counts and function are normal., Interpretation: In-utero transplantation of haematopoietic progenitor cells allowed immune reconstitution of a fetus with SCIDXI and may be an alternative to elective abortion. Our report should encourage applications of this method to other inherited disorders curable by BMT.

Adenosine deaminase (ADA) deficiency results in severe combined immunodeficiency, the first genetic disorder treated by gene therapy. Two different retroviral vectors were used to transfer ex vivo the human ADA minigene into bone marrow cells and peripheral blood lymphocytes from two patients undergoing exogenous enzyme replacement therapy. After 2 years of treatment, long-term survival of T and B lymphocytes, marrow cells, and granulocytes expressing the transferred ADA gene was demonstrated and resulted in normalization of the immune repertoire and restoration of cellular and humoral immunity. After discontinuation of treatment, T lymphocytes, derived from transduced peripheral blood lymphocytes, were progressively replaced by marrow-derived T cells in both patients. These results indicate successful gene transfer into long-lasting progenitor cells, producing a functional multilineage progeny.

Bone marrow transplantation (BMT) using HLA-partially matched family donors has produced disappointing results (25-30% of long-term survivors) in patients with severe aplastic anemia. We describe two children affected by severe aplastic anemia, not responsive to immunosuppressive therapy, who underwent allogeneic bone marrow transplantation using a HLA-partially matched family donor. Both cases presented 2 first class HLA-antigens (A and B) disparity between donor and recipient. The pretransplant conditioning regimen consisted of cyclophosphamide, thoracoabdominal irradiation, cytosine-arabinoside, and antilymphocyte globulin. As graft versus host disease (GVHD) prophylaxis, Cyclosporine-A was administered at usual dosages for 6 months. A full marrow engraftment was observed in both cases. Only grade I acute GVHD, promptly responsive to corticosteroid therapy, developed with no chronic GVHD. Five months after transplant, both children progressively developed hypertension, renal function impairment, thrombocytopenia, and severe normochromic anemia, with erythropoietin serum levels lower than expected for the haematocrit. After antihypertension treatment and supportive therapy, the clinical picture progressively improved, while treatment with recombinant human erythropoietin completely corrected the long-lasting anemia. The two children are alive and well 28 months after the transplant, with a Karnofsky score of 100% and a normal peripheral blood count. The authors suggest that, once immunosuppressive therapy has failed, BMT from donors other than HLA-identical sibling is a feasible approach in children affected by severe aplastic anemia, not having an HLA-identical donor.

The pattern of X-chromosome inactivation was analyzed, by means of two different DNA probes (pSPT-PGK and M27 beta), in several cell lineages derived from females belonging to a pedigree with X-linked immunodeficiency with hyper-IgM (HIGM1). Non-random X-chromosome inactivation was demonstrated in T cells, B cells, and neutrophils, but not in fibroblasts, of obligate carriers, suggesting that different hematopoietic cell lineages are primarily involved in HIGM1. Preferential inactivation of the paternally derived X-chromosome was demonstrated by analysis of segregation of the alleles defined by the pSPT-PGK and M27 beta probes. The possibility that the HIGM1 mutation may confer a proliferative and/or differential advantage to hematopoietic precursors carrying the mutated allele on the active X-chromosome is discussed.

In the last fifteen years, therapeutic use of intravenous immunoglobulin on one hand, and of bone marrow transplantation on the other, have largely modified survival rate and prognosis for many primary immunodeficiency diseases. At the same time, major advances in molecular genetics have allowed mapping of several immunodeficiency genes and made prenatal diagnosis feasible. Furthermore, for many X-linked immunodeficiencies, carrier detection can be also accomplished by means of analysis of the pattern of X-chromosome inactivation. As a whole, these techniques have substantially contributed to a more accurate genetic counseling in the families.

BMT can cure several congenital immunological defects: if in these disease the engrafting is easier, the GVH reactions are more frequent and severe. The possibility to deplete from T lymphocyte the marrow before infusion, has overcame this difficulty. From 1968 183 BMT have been performed in Europe on patients with SCID (70 from HLA-identical donor, 113 from HLA-nonidentical donor). The survival after 2 years is 76% in the first group, and 56% in the second group (100 marrows have been T-depleted with different techniques). Strict isolation procedures before the transplant are very important to achieve good results. The possibility to treat different immunodeficiency With BMT are also discussed.