Immunodeficiency, autoinflammation and amylopectinosis in humans with inherited HOIL-1 and LUBAC deficiency

We report the clinical description and molecular dissection of a new fatal human inherited disorder characterized by chronic auto-inflammation, invasive bacterial infections and muscular amylopectinosis. Patients from two kindreds carried biallelic loss-of-expression and loss-of-function mutations in HOIL1, a component 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 hyperresponsive 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 auto-inflammation and immunodeficiency in these patients. These data suggest that LUBAC regulates NF-κB-dependent IL-1β responses differently in different cell types.

A single-center experience in 20 patients with infantile malignant osteopetrosis

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.

Stem cell transplantation for primary immunodeficiencies

BMT is curative in almost 75% of children affected by severe primary immunodeficiencies (PIDs). Recently, the chance of cure has increased thanks to the availability of matched unrelated donors (MUDs). Nevertheless, besides the conventional indications to BMT (profound or absent T-cell function, profound or absent natural killer function, known syndromes with T-cell deficiencies), indications to BMT for PIDs affecting the quality of life or having an expectation of life that does not exceed the third-fourth decade remain unclear. Infact, if it is evident that the survival rate in an infant grafted for a PID with a MUD is expected to be more than 80%, alternative treatments such as gene therapy are now available.

Genetic causes of bronchiectasis: primary immune deficiencies and the lung

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.

Long-term outcome following hematopoietic stem-cell transplantation in Wiskott-Aldrich syndrome: collaborative study of the European Society for Immunodeficiencies and European Group for Blood and Marrow Transplantation

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.

Lack of iNKT cells in patients with combined immune deficiency due to hypomorphic RAG mutations

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.

Long-term immune reconstitution and clinical outcome after stem cell transplantation for severe T-cell immunodeficiency

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.

Stem cell transplantation in primary immunodeficiencies

PURPOSE OF REVIEW

To review indications and outcomes of haematopoietic stem cell transplantation in primary immunodeficiencies, in light of recent advances in the field.

RECENT FINDINGS

Remarkable improvements in the outcome of haematopoietic stem cell transplantation in primary immunodeficiencies have recently been reported. This is a result of the successful use of alternative donors and more effective strategies to prevent and treat complications. These advances have now permitted the indications for haematopoietic stem cell transplantation to be extended in primary immunodeficiencies.

SUMMARY

The optimal results of haematopoietic stem cell transplantation in primary immunodeficiencies have long been obtained with related human leukocyte antigen-identical donors, an option limited to a minority of patients. Transplantation from mismatched related donors has been used with good results mainly in infants with severe combined immune deficiency, but has been associated with significantly delayed or incomplete immune reconstitution. Recent data indicate that transplantation from matched unrelated donors and cord blood transplantation represent valid alternatives, which can be used in all forms of severe primary immunodeficiencies. This, along with careful monitoring of infections, coupled with preemptive treatment, has resulted in a significant improvement in the outcome of haematopoietic stem cell transplantation for severe forms of primary immunodeficiencies.

Stem cell transplantation for the Wiskott-Aldrich syndrome: a single-center experience confirms efficacy of matched unrelated donor transplantation

The treatment of Wiskott-Aldrich syndrome (WAS), a once uniformly fatal disorder, has evolved considerably as the use of hematopoietic stem cell transplant has become more widespread. For the majority of patients who lack an human leukocyte antigen-identical sibling, closely matched unrelated donor bone marrow transplant (MUD BMT) at an early age is an excellent option that nevertheless is not uniformly chosen. We retrospectively analyzed our experience with transplantation in 23 patients with WAS from 1990 to 2005 at the University of Brescia, Italy, of whom 16 received MUD BMT. Myeloablative chemotherapy was well tolerated with median neutrophil engraftment at day 18, and no cases of grade III or IV graft-vs-host disease. Overall survival was very good with 78.2% (18/23) of the whole cohort and 81.2% (13/16) of MUD BMT recipients surviving. Among 18 survivors, full donor engraftment was detected in 12 patients, and stable mixed chimerism in all blood lineages in four patients. Deaths were limited to patients who had received mismatched related BMT or who had severe clinical symptomatology at the time of transplantation, further emphasizing the safety and efficacy of MUD BMT when performed early in the clinical course of WAS.

Bone marrow transplantation for severe combined immune deficiency

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.

Cytokine-mediated signalling and early defects in lymphoid development

PURPOSE OF REVIEW

The aim of the review is to report on recent advances in cytokine-mediated signalling, as illustrated by the study of natural human mutants. In particular, the role of cytokines and cytokine-mediated signalling in human T-cell development is analysed in detail, and currently available forms of treatment including experimental trials are described.

RECENT FINDINGS

Defects of the cytokine/JAK/STAT axis have been recently described as responsible for human Severe Combined Immune Deficiency. In particular, defects in gammac, JAK3 and IL7RA have been analysed in terms of development of novel diagnostic tools as well as of new therapeutic agents for the treatment of autoimmune diseases and graft-versus-host disease.

SUMMARY

Dissection of the genetic defects underlying the various forms of Severe Combined Immune Deficiency has helped develop new and more accurate diagnostic assays and novel forms of treatment.

Hematopoietic stem cell transplantation in Omenn syndrome: a single-center experience

We retrospectively analyzed the outcome of hematopoietic stem cell transplantations (HSCT) performed at our Center between 1991 and 2002 in 11 unselected patients with Omenn syndrome, a variant of severe combined immunodeficiency. The patients' mean age at the time of the first HSCT was 8.4 months. Two patients received two, and one patient three, HSCT procedures. The resulting 15 HSCT derived in seven cases from HLA-haploidentical parents, in four patients from matched unrelated donors, in three cases from an HLA phenotypically identical related donor, and in one case from an HLA genotypically identical family donor. Nine out of 11 patients are alive and immunoreconstituted 30-146 months after transplantation. At the time of the most recent evaluation, all of the nine survivors had normal T-cell function, and eight of them had developed normal antibody production. This study demonstrates an overall mortality of 18.2%, which is substantially lower than previously reported. Early recognition of OS, rapid initiation of adequate supportive treatment and HSCT lead to improved outcome for this otherwise fatal disease, regardless of the origin and matching of hematopoietic stem cells.

AIRE deficiency in thymus of 2 patients with Omenn syndrome

Omenn syndrome is a severe primary immunodeficiency with putative autoimmune manifestations of the skin and gastrointestinal tract. The disease is caused by hypomorphic mutations in recombination-activating genes that impair but do not abolish the process of VDJ recombination, leading to the generation of autoreactive T cells with a highly restricted receptor repertoire. Loss of central tolerance in genetically determined autoimmune diseases, e.g., autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy, is associated with defective expression by medullary thymic epithelial cells of AIRE, the transcription activator that induces thymic expression of tissue-specific antigens. Analysis of AIRE expression in the thymi of 2 Omenn syndrome patients and 1 SCID patient, by real-time RT-PCR and immunohistochemistry, demonstrated a profound reduction in the levels of AIRE mRNA and protein in patients as compared with a normal control subject. Lack of AIRE was associated with normal or even increased levels of keratin and lymphotoxin-beta receptor mRNAs, while mRNAs of the self-antigens insulin, cytochrome P450 1a2, and fatty acid-binding protein were undetectable in thymi from immunodeficiency patients. These results demonstrate that deficiency of AIRE expression is observed in severe immunodeficiencies characterized by abnormal T cell development and suggest that in Omenn syndrome, the few residual T cell clones that develop may escape negative selection and thereafter expand in the periphery, causing massive autoimmune reactions.

Interleukin-7 receptor alpha (IL-7Ralpha) deficiency: cellular and molecular bases. Analysis of clinical, immunological, and molecular features in 16 novel patients

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.

AIRE and immunological tolerance: insights from the study of autoimmune polyendocrinopathy candidiasis and ectodermal dystrophy

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.

Reconstitution of T-cell compartment after in utero stem cell transplantation: analysis of T-cell repertoire and thymic output

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.

Altered leukocyte response to CXCL12 in patients with warts hypogammaglobulinemia, infections, myelokathexis (WHIM) syndrome

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.

Serum osteoprotegerin and receptor activator of nuclear factors kB (RANKL) concentrations in normal children and in children with pubertal precocity, Turner's syndrome and rheumatoid arthritis

BACKGROUND

Osteoprotegerin (OPG) is a secreted member of the TNF receptor superfamily. OPG is made by osteoblastic cells and is expressed in a wide variety of cell and tissue types. It acts as a decoy receptor by binding the receptor activator of nuclear factors kB (RANKL) and preventing RANKL-induced osteoclast formation and differentiation. Numerous cytokines and hormones (TGF-beta, PTH, vitamin D, glucocorticoids and oestrogens) exert their effects on osteoclastogenesis by regulating the production of OPG.

PATIENTS AND METHODS

In the present study we compared serum OPG and RANKL concentrations in a group of normal children (1-14 years old) with those of pair-aged children affected by different diseases [Turner's syndrome (TS), early/precocious puberty (PP) and rheumatoid arthritis (RA)]. OPG and RANKL concentrations were measured by an enzyme immunoassay method using a commercial kit.

RESULTS

Mean (+/- SD) OPG level in normal children was 4.05 +/- 1.63 pmol/l with no difference between males and females. OPG values in children 1-4 years old (5.87 +/- 2.22 pmol/l) were significantly higher than in children 4-14 years old (3.55 +/- 0.97 pmol/l). OPG levels in children with RA were significantly higher than in controls (6.33 +/- 2.57 pmol/l vs. 4.05 +/- 1.63 pmol/l, P < 0.01); patients with TS or PP had OPG levels superimposable to those of controls (2.61 +/- 0.67 pmol/l and 3.99 +/- 0.85 pmol/l, respectively), but in TS OPG levels were significantly lower than in age-matched females. Mean RANKL concentration in normal subjects was 0.81 +/- 1.55 pmol/l; there was a slight decline in RANKL levels with age. RANKL concentrations in subjects with TS, PP, RA and controls did not differ significantly, and did not differ from those published in adult normal subjects.

CONCLUSIONS

It appears from our data that OPG serum levels in healthy children aged > 4 years are similar to those present in young adult men, with higher levels in the first 4 years of life. Although the meaning of the alterations of OPG levels observed in pathological conditions is still obscure, they appear potentially interesting in view of a key role played by this protein in bone homeostasis.

Treatment of CD40 ligand deficiency by hematopoietic stem cell transplantation: a survey of the European experience, 1993-2002

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.

Impact of marrow unrelated donor search duration on outcome of children with acute lymphoblastic leukemia in second remission

We analyzed the outcome of 167 consecutive children with second CR acute lymphoblastic leukemia (ALL), for whom an unrelated donor (UD) search was activated between 1989 and 1998 at a median time of 2 months after relapse. A suitable donor was identified for 70 patients at 1 year and 6.5 months before and after 1995 from search activation, respectively; a further leukemia relapse occurred during the search in 94 children at a median of 4 months after search activation, 36 of whom underwent UD (14) or other types of transplant (22), beyond second CR, while 58 died of progressive disease. Of 73 patients not experiencing a second relapse, 64 underwent UD (46) or other types of transplant (18), while nine proceeded with chemotherapy, and only four of them survived. The 3-year disease-free survival (DFS) from second CR for the 167 patients is 15.1%, whereas 3-year DFS after transplant for the 60 UD and 40 alternative donor transplanted children is 31.6 and 25.4%, respectively. In conclusion, a further relapse is the main factor adversely affecting outcome of children with second CR ALL. Thus, for these patients, the search should be activated early after relapse and either a UD or an alternative transplant should be performed as early as possible.

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.

Primary immune deficiencies unravel the molecular basis of immune response

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.

Unrelated donor marrow transplantation in childhood: a report from the Associazione Italiana Ematologia e Oncologia Pediatrica (AIEOP) and the Gruppo Italiano per il Trapianto Midollo Osseo (GITMO)

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.

V(D)J recombination defects in lymphocytes due to RAG mutations: severe immunodeficiency with a spectrum of clinical presentations

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.

Of genes and phenotypes: the immunological and molecular spectrum of combined immune deficiency. Defects of the gamma(c)-JAK3 signaling pathway as a model

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.

Haploidentical peripheral blood and marrow stem cell transplantation in nine cases of primary immunodeficiency

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 immunodeficiencies due to defects in signal transduction: defects of the gammac-JAK3 signaling pathway as a model

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.

Development of autologous T lymphocytes in two males with X-linked severe combined immune deficiency: molecular and cellular characterization

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.

[Prenatal and postnatal transplantation of hematopoietic stem cells in children with primary immunodeficiency]

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.

Development of autologous, oligoclonal, poorly functioning T lymphocytes in a patient with autosomal recessive severe combined immunodeficiency caused by defects of the Jak3 tyrosine kinase

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.

In-utero transplantation of parental CD34 haematopoietic progenitor cells in a patient with X-linked severe combined immunodeficiency (SCIDXI)

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.

Gene therapy in peripheral blood lymphocytes and bone marrow for ADA- immunodeficient patients

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.

Successful bone marrow transplantation in children with severe aplastic anemia using HLA-partially matched family donors

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.

Insulin-dependent diabetes mellitus and severe atopic dermatitis in a child with adenosine deaminase deficiency

We report a 2.3-year-old girl with complete lack of adenosine deaminase (ADA) activity who presented with severe atopic dermatitis and insulin-dependent diabetes mellitus but only mild recurrent infections. Abnormalities of immune function included profound depletion of CD8+ lymphocytes, hyperimmunoglobulinaemia E, and very low in vitro proliferative response to mitogens. Treatment with polyethylene glycol-conjugated ADA was followed by rapid amelioration of clinical and immunological conditions. The immunological and clinical features of this child suggest that the clinical spectrum of ADA deficiency may be broader than originally supposed.

Analysis of X-chromosome inactivation in X-linked immunodeficiency with hyper-IgM (HIGM1): evidence for involvement of different hematopoietic cell lineages

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.

[Primary immunodeficiency 1991: new uses and prospects of genetic counseling]

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.

[Bone marrow transplantation in congenital defects of immunity]

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.