Clinical spectrum of X-linked hyper-IgM syndrome

Primary Immunodeficiencies

Primary immunodeficiencies (PIDs), once considered to be very rare, are now increasingly recognized because of growing knowledge in the immunological field and the availability of more sophisticated diagnostic techniques and therapeutic modalities [161]. However in a database of >120,000 inpatients of a general hospital for conditions suggestive of ID 59 patients were tested, and an undiagnosed PID was found in 17 (29%) of the subjects tested [107]. The publication of the first case of agammaglobulinemia by Bruton in 1952 [60] demonstrated that the PID diagnosis is first done in the laboratory. However, PIDs require specialized immunological centers for diagnosis and management [33]. A large body of epidemiological evidence supports the hypothesis of the existence of a close etiopathogenetic relation between PID and atopy [73]. In particular, an elevated frequency of asthma, food allergy (FA), atopic dermatitis and enteric pathologies can be found in various PIDs. In addition we will discuss another subject that is certainly of interest: the pseudo-immunodepressed child with recurrent respiratory infections (RRIs), an event that often requires medical intervention and that very often leads to the suspicion that it involves antibody deficiencies [149].

Premature labor: a state of platelet activation?

OBJECTIVE

This study was undertaken to determine whether premature labor is associated with changes in the maternal plasma concentration of soluble CD40 ligand (sCD40L), a marker of platelet activation.

METHODS

A cross-sectional study included patients in the following groups: 1) non-pregnant (n=21); 2) normal pregnancy (n=71); 3) normal pregnancy at term with (n=67) and without labor (n=88); 4) preterm labor (PTL) with intact membranes (n=136) that was divided into the following sub-groups: 4a) PTL who delivered at term (n=49); 4b) PTL without intra-amniotic infection and/or inflammation (IAI) who delivered preterm (n=54); and 4c) PTL with IAI who delivered preterm (n=33). sCD40L concentrations were measured by ELISA.

RESULTS

The median maternal plasma sCD40L concentration was higher in pregnant than non-pregnant women (P=0.017). Patients with PTL had a higher median maternal plasma sCD40L concentration than women with normal pregnancies, regardless of the presence or absence of IAI and gestational age at delivery (P<0.001 for all comparisons). IAI was not associated with a higher median maternal plasma concentration of sCD40L.

CONCLUSIONS

Normal pregnancy is a state in which there is a physiologic increase of sCD40L. PTL was associated with an increased median maternal plasma sCD40L concentration that could not be accounted for by IAI. Thus, our findings suggest that platelet activation occurs during an episode of preterm labor.

Tolerance and autoimmunity: lessons at the bedside of primary immunodeficiencies

The recent progress in the genetic characterization of many primary immunodeficiencies (PIDs) allows for a better understanding of immune molecular and cellular mechanisms. The present chapter discusses associations between PIDs and autoimmune diseases (AIDs) in this new light. PIDs are classified according to the frequency of association with AIDs, defining four groups of conditions: systematic (more than 80% of all patients), strong (10-80%), mild (less than 10%), and absent (no available descriptions). Several general conclusions could be drawn: (1) pathological autoimmune (AI) manifestations are very frequently associated with PIDs, indicating that, contrary to conventional notions, antimicrobial protection and natural tolerance to body tissues share many basic mechanisms; (2) in some gene defects, association is so strong that one could speak of "monogenic" AIDs; (3) basic types of PIDs are selectively associated with AID of a particular set of target tissues; (4) while for some gene defects, current theory satisfactorily explains pathogenesis of the corresponding AID, other situations suggest extensive gaps in the present understanding of natural tolerance; and (5) not exceptionally, observations on the AI phenotype for the same gene defect in mouse and man are not concordant, perhaps owing to the limited genetic diversity of mouse models, often limited to a single mouse strain. Overall, clinical observations on PID support the new paradigm of "dominant" tolerance to self-components, in which AID owes to deficits in immune responses (i.e., in regulatory mechanisms), rather than from excessive reactivity.

A molecular classification of congenital neutropenia syndromes

Current knowledge on the molecular pathogenesis of severe congenital neutropenia indicates that the clinical diagnosis includes a heterogeneous group of disorders following different patterns of inheritance. Similarly, multifaceted syndromes associated with neutropenia can be classified molecularly, which in turn allows for a better understanding of the basis of the neutropenia. Many of the neutropenia disorders can be treated with G-CSF (filgrastim) to increase the neutrophil count, thereby reducing infection morbidity and mortality. In some instances hematopoietic stem cell transplantation remains the only curative treatment currently available. This review describes and classifies, on a molecular basis, both primary congenital neutropenia and multifaceted syndromes associated with neutropenia.

Mycobacterial infections in primary immunodeficiency patients

Primary immunodeficiencies (PID) are a diverse group of hereditary diseases leading to the impaired immune response that creates high susceptibility to mycobacterium infection. High susceptibility to mycobacterial infections of patients suffering from defects of phagocytosis and combined immunodeficiencies can be explained by predominant participation of macrophages and T lymphocytes in the specific immune response. Mycobacterium tuberculosis, Bacille Calmette-Guerin, and non-tuberculosis mycobacterium (NTM) may cause a severe disease in patients with PIDs. We report here our results of the clinical features of mycobacterium infection presentations in 36 patients with various PIDs.

Cryptosporidium infection in patients with primary immunodeficiencies

BACKGROUND

Cryptosporidium species infection is usually self-limited in immunocompetent populations, but can be severe and life-threatening among immunocompromised individuals, particularly in patients with AIDS and in these patients with primary immunodeficiencies (PIDs).

PATIENTS AND METHODS

A group of 5 patients with genetically confirmed hyper-IgM syndrome type 1 (XHIM) and one patient with primary CD4 lymphopenia were enrolled in the study. At least 2 stool samples and a bile sample in one patient were examined for Cryptosporidium oocysts by a modified Ziehl-Neelsen technique, by immunofluorescence assay using a commercial kit, as well as by molecular analysis followed by genotyping. Immunological status at the time of PID diagnosis and the complex picture of disease are presented.

RESULTS

Chronic cryptosporidiosis was confirmed in 3 patients with XHIM and in one patient with primary CD4 lymphopenia. Molecular diagnosis showed the presence of C parvum, C hominis, and C meleagridis in analyzed specimens.

CONCLUSIONS

Cryptosporidium infection with serious clinical symptoms observed in patients with hyper-IgM syndrome calls for regular, repeated screening in this group of patients.

X-linked hyper-IgM syndrome associated with poorly differentiated neuroendocrine tumor presenting as obstructive jaundice secondary to extensive adenopathy

X-Linked Hyper IgM Syndrome (XHIGM) is a rare B-cell immunodeficiency disease. Patients with XHIGM are unable to switch immunoglobulin production from IgM to IgG, IgA, and IgE. Patients with XHIGM require periodic intravenous immune globulin to help prevent infections, and are also at risk for a variety of neoplasms. We describe a young man with XHIGM who presented with obstructive jaundice from malignant adenopathy from widespread, poorly differentiated neuroendocrine tumor. This has not previously been reported and represents a new association with XHIGM.

CHARGE Association, Hyper-Immunoglobulin M Syndrome, and Conjunctival MALT Lymphoma

PURPOSE

To report a case of a 5-year-old child with CHARGE association and bilateral conjunctival mucosa-associated lymphoid tissue (MALT) lymphoma treated with topical interferon-alpha.

METHODS

Case report.

RESULTS

A 5-year-old girl, diagnosed with nonclassical CHARGE association and hyper-immunoglobulin M (IgM) syndrome, was referred with a 2-month history of suspected purulent bilateral streptococcal conjunctivitis. Clinical symptoms did not resolve despite multiple antibiotic treatments, and her clinical course was attributed to underlying immunodeficiency. Biomicroscopy showed salmon-colored, nodular lesions occupying both fornices and caruncles. Inferior conjunctival biopsy was performed, and MALT lymphoma was diagnosed. Bilateral treatment was initiated with topical interferon-alpha, applied 3 times a day at a concentration of 5 x 10 U/m/d, for 4 months. Complete regression of symptoms and conjunctival lesions was achieved. No recurrences have been observed after 1-year follow-up.

CONCLUSIONS

We report the use of topical interferon-alpha as treatment for bilateral conjunctival MALT lymphoma in a young child with CHARGE association and hyper-IgM syndrome.

CD40 ligand and MHC class II expression are essential for human peripheral B cell tolerance

Hyper-IgM (HIGM) syndromes are primary immunodeficiencies characterized by defects of class switch recombination and somatic hypermutation. HIGM patients who carry mutations in the CD40-ligand (CD40L) gene expressed by CD4⁺ T cells suffer from recurrent infections and often develop autoimmune disorders. To investigate the impact of CD40L–CD40 interactions on human B cell tolerance, we tested by ELISA the reactivity of recombinant antibodies isolated from single B cells from three CD40L-deficient patients. Antibody characteristics and reactivity from CD40L-deficient new emigrant B cells were similar to those from healthy donors, suggesting that CD40L–CD40 interactions do not regulate central B cell tolerance. In contrast, mature naive B cells from CD40L-deficient patients expressed a high proportion of autoreactive antibodies, including antinuclear antibodies. Thus, CD40L–CD40 interactions are essential for peripheral B cell tolerance. In addition, a patient with the bare lymphocyte syndrome who could not express MHC class II molecules failed to counterselect autoreactive mature naive B cells, suggesting that peripheral B cell tolerance also depends on major histocompatibility complex (MHC) class II–T cell receptor (TCR) interactions. The decreased frequency of MHC class II–restricted CD4⁺ regulatory T cells in CD40L-deficient patients suggests that these T cells may mediate peripheral B cell tolerance through CD40L–CD40 and MHC class II–TCR interactions.

CD40-CD40L interaction in immunity against protozoan infections

Activation of the immune system against protozoan infections relies particularly on two specific signals provided by cognate interaction of T cells with antigen presenting cells (APCs). The first signal is attributed to binding of the T-cell receptor (TCR) to peptide/MHC complexes on the surface of APCs, whereas the second signal is triggered through binding of several costimulatory molecules on the surface of APCs with their corresponding receptors on T cells. Among these costimulatory signallings, CD40/CD40L interactions have been particularly investigated in protozoan infection models with regard to their potential to amplify cell-mediated immunity against intracellular parasites. This article reviews current studies of the potential role of CD40/CD40L interaction in the modulation of immune responses against some protozoan parasites and highlights recent developments regarding manipulation of this interaction for promoting control of parasite infections.

Clinical follow-up of 11 Argentinian CD40L-deficient patients with 7 unique mutations including the so-called "milder" mutants

CD40 ligand (CD40L) deficiency is an X-linked combined immunodeficiency characterized by impaired class switch recombination. We analyzed clinical and molecular findings in 11 Argentinian patients from seven unrelated families. The mean age at onset of symptoms was 1.1 years (0.5-3.0 years) and the 10 alive patients have a median age of 17 years. We identified two nonsense mutations, including R11X reported as a "hypomorphic" defect, four missense mutations, and one point deletion. Although R11X was associated herein with parvovirus B19-anemia and higher Igs levels as previously described, histoplasmosis and Pneumocystis jiroveci pneumonia were also present. Other so-called "milder" mutation, T254M, was present in three related patients clinically and immunologically undistinguishable from the rest of the cohort. Furthermore, 10 of the 11 patients, having heterogeneous mutations, never had persistent neutropenia, none presented Cryptosporidium sp. infection nor developed liver-biliary tract disease, highlighting the debatable concept of "milder" mutations.

Osteopenia in X-linked hyper-IgM syndrome reveals a regulatory role for CD40 ligand in osteoclastogenesis

We report that osteopenia is a prominent and previously unappreciated clinical feature of patients with X-linked hyper-IgM syndrome, an inherited immune deficiency disorder caused by mutations in the gene encoding CD40 ligand (CD40L). We therefore conducted studies to determine the relationship between CD40L and osteoclastogenesis. Recognizing that activated T cells express surface receptor activator of NF-kappaB ligand (RANKL) and can induce osteoclast differentiation of myeloid cells expressing RANK, we assessed the capacity of wild-type T cells and CD40L(-/-) T cells to induce osteoclastogenesis in vitro. Relative to wild-type T cells, activated CD40L(-/-) T cells from both humans and mice promoted robust osteoclast differentiation of myeloid cells. Whereas activated CD40L(-/-) T cells had normal expression of RANKL, they were deficient in IFN-gamma production. In subsequent studies, we cultured activated CD40L(-/-) T cells in the presence of IFN-gamma, and we found that the osteoclastic capacity of CD40L(-/-) T cells could be greatly diminished. These results show that CD40L can influence RANKL signaling through T cell priming, and thus they demonstrate a regulatory role for CD40L in bone mineralization that is absent in patients with X-linked hyper-IgM syndrome.

The structural basis of hyper IgM deficiency – CD40L mutations

X-linked hyper-IgM syndrome (XHIGM) is a primary immunodeficiency characterised by an inability to produce immunoglobulins of the IgG, IgA and IgE isotypes. It is caused by mutations of CD40 ligand (CD40L, CD154), expressed on T-lymphocytes. The interaction of CD40L on T-cells and its receptor CD40 on B-cells is essential for lymphocyte signalling leading to immunoglobulin class switching and B-cell maturation. To understand the structural basis for XHIGM, we utilised bioinformatics methods to analyse all the known CD40L missense mutations at both the sequence and structural level. Our results demonstrate that the 35 different missense mutations have diverse effects on CD40L structure and function, affecting structural disorder and aggregation tendencies, stability maintaining contacts and electrostatic properties. Several mutations also affect residues essential in receptor binding and trimerisation. Experimental study of effects of mutations is laborious and time-consuming and at the structural level often almost impossible. By contrast, precise and useful information about effects of mutations on protein structure and function can readily be obtained by theoretical methods. In this study, all the XHIGM causing missense mutations could be explained in terms of CD40L structure and function. Thus, the molecular basis of the syndrome could be elucidated.

Role of CD40-Dependent Down-Regulation of CD154 in Impaired Induction of CD154 in CD4+ T Cells from HIV-1-Infected Patients

CD40-CD154 interaction is pivotal for cell-mediated immunity. There are contradictory reports on whether HIV-1 infection impairs CD154 induction. The interaction between CD40 and CD154 is important not only because it results in activation of APCs but also because it controls CD154 by diminishing expression of this molecule. Compared with healthy controls, CD4(+) T cells from HIV-1(+) patients had impaired induction of CD154 when T cell activation was mediated by CD40(+) APCs. In contrast, T cell activation in the absence of these cells resulted in normal CD154 expression. CD154 induction in HIV-1(+) patients and controls were similar upon blockade of CD40-CD154 binding. Defective regulation of CD154 appeared to occur downstream of the control of mRNA levels because up-regulation of CD154 mRNA was not impaired by HIV-1 infection. This work identifies CD40 as a mediator of impaired CD154 induction in HIV-1 infection and explains why this defect was not detected by studies where T cell activation was triggered independently of CD40(+) APCs. In addition, dysregulation of CD154 in HIV-1 infection likely contributes to immunodeficiency because diminished expression of CD154 induced by CD40 is of functional relevance, resulting in decreased dendritic cell maturation.

Hyper-immunoglobulin M syndrome caused by a mutation in the promotor for CD40L

Hyper-immunoglobulin M (IgM) syndrome (HIGM) is a rare primary immunodeficiency characterized by elevated or normal IgM and absent or markedly decreased amounts of IgG, IgA and IgE. The X-linked form (HIGM1) is the most common type and is caused by mutations in the gene for CD40L, a T-cell surface molecule required for T-cell driven immunoglobulin class switching by B cells. In the present study we have identified a patient with X-linked hyper-IgM who failed to express CD40L on the cell surface of CD4(+) T lymphocytes. Sequence analysis of CD40L genomic DNA showed no mutations. CD40L mRNA was absent and sequence analysis of the CD40L promotor revealed a mutation at position -123 from the transcription start site. The mutation in the promotor region likely contributed to the decreased transcription as demonstrated by a luciferase reporter assay.

Class switch recombination: a comparison between mouse and human

Humans and mice separated more than 60 million years ago. Since then, evolution has led to a multitude of changes in their genomic sequences. The divergence of genes has resulted in differences both in the innate and adaptive immune systems. In this chapter, we focus on species difference with regard to immunoglobulin class switch recombination (CSR). We have compared the immunoglobulin constant region gene loci from human and mouse, with an emphasis on the switch regions, germ line transcription promoters, and 3' enhancers. We have also compared pathways/factors that are involved in CSR. Although there are remarkable similarities in the cellular machinery involved in CSR, there are also a number of unique features in each species.

Phylogenetic analysis of the promoter region of the CD40L gene in primates and other mammals

CD40L is a type II membrane protein comprised of 261 amino acids. CD40L plays a crucial role in the immune system where it is primarily expressed on activated T cells and triggers immunoglobulin class switching. The genetic disease X-linked hypergammaglobulinemia (HIGM1, XHIGM or XHIM) is caused by mutations in the CD40L gene. Individuals with HIGM1 are susceptible to recurrent infections to pathogens and a relationship has been shown to exist with malaria [Sabeti, P., Usen, S., Farhadian, S., Jallow, M., Doherty, T., Newport, M., Pinder, M., Ward, R., Kwiatkowski, D., 2002a. CD40L association with protection from severe malaria. Genes Immun. 3, 286-291]. In this paper, we phylogenetically examine the promoter region of CD40L in primates and other mammals via phylogenetic shadowing. This analysis revealed several regions of the CD40L promoter that were highly constrained and thereby inferred to be functional. These constrained regions confirmed many known regulatory sites. In addition, a novel, highly constrained upstream region was also identified which had an NF-AT recognition motif. These analyses also showed that the different mammal groups do not share an exactly similar set of promoter binding sites and taxon-specific promoters have evolved.

Primary immunodeficiencies and susceptibility to parasitic infections

Primary immunodeficiencies are important disorders because they typically cause severe illness in affected patients. In addition, these diseases provide a unique glimpse at the underpinnings of the immune system in humans. Susceptibility to infections, including those caused by parasites, is a hallmark of these immune defects. Understanding the association between primary immunodeficiencies and parasitic infections will likely improve our grasp on the mechanisms of defense against these pathogens.

Inborn errors of IL-12/23- and IFN-γ-mediated immunity: molecular, cellular, and clinical features

Mendelian susceptibility to mycobacterial diseases confers predisposition to clinical disease caused by weakly virulent mycobacterial species in otherwise healthy individuals. Since 1996, disease-causing mutations have been found in five autosomal genes (IFNGR1, IFNGR2, STAT1, IL12B, IL12BR1) and one X-linked gene (NEMO). These genes display a high degree of allelic heterogeneity, defining at least 13 disorders. Although genetically different, these conditions are immunologically related, as all result in impaired IL-12/23-IFN-gamma-mediated immunity. These disorders were initially thought to be rare, but have now been diagnosed in over 220 patients from over 43 countries worldwide. We review here the molecular, cellular, and clinical features of patients with inborn errors of the IL-12/23-IFN-gamma circuit.

Common variable immunodeficiency. Old questions are getting clearer

Common variable immunodeficiency (CVID) is a heterogeneous entity characterized by an impaired ability to produce antibodies. The failure is localized in partially mature B lymphocytes, though T lymphocyte abnormalities are occasionally present. This deficiency affects antibody synthesis and class switch from IgD and IgM, to IgG and IgA. CVID is related to selective IgA deficiency, and both abnormalities may coincide in one same family, and evolve from one to another in the same patient. The symptoms generally manifest in adults, but can occur at any age, even in infancy. Recurrent bacterial infections or pneumonias are frequent, and may be complicated by gastrointestinal problems, granulomas, autoimmune disorders or malignancies. A defect in memory B cells seems to condition the clinical severity. Recently, several mutations in genes encoding for molecules (CD19, TACI, ICOS) involved in B cell survival and isotype switch have been identified in patients with CVID. Nevertheless, genetic abnormalities have been found in less than 25 % of cases with CVID; the underlying mechanism thus remains unknown in the majority of CVID patients, and research in this field must continue.

Bone marrow transplantation for cartilage-hair-hypoplasia

The association of cartilage hair hypoplasia (CHH) with severe combined immunodeficiency (SCID) has been known for more than three decades. Bone marrow transplantation (BMT) remains the only effective treatment that might cure SCID. Surprisingly little has been reported on the experience with BMT in CHH. We report here survival and long-term reconstitution of immunity after BMT in three patients with CHH. Regardless of whether a related human leukocyte antigen-matched or unrelated matched donors were used as the source of BMT, all patients are alive and well 5-20 years after BMT. Engraftment appears robust with most cells of donors origin. Repeated evaluation of the immune system showed normal cellular and humoral immunity. Our results should encourage the use of BMT in patients with CHH who have profound immunodeficiency.

T Cell-Dependent Activation of Dendritic Cells Requires IL-12 and IFN-γ Signaling in T Cells

Patients presenting with genetic deficiencies in IFNGR1, IFNGR2, IL-12B, and IL-12RB1 display increased susceptibility to mycobacterial infections. We analyzed in this group of patients the cross-talk between human CD4+ T lymphocytes and dendritic cells (DCs) that leads to maturation of DC into producers of bioactive IL-12 and to activation of T cells into IFN-gamma producers. We found that this cross-talk is defective in all patients from this group. Unraveling the mechanisms underlying this deficiency, we showed that IL-12 signaling in T cells is required to induce expression of costimulatory molecules and secretion of IL-12 by DCs and that IFNGR expression is required on both DCs and CD4+ T cells to induce IL-12 secretion by DCs. These data suggest that CD4+ T cell-mediated activation of DCs plays a critical role in the defense against mycobacterial infections in humans.

Cellular and genetic basis of primary immune deficiencies

Knowledge of the genetic mutations of primary immune deficiency syndromes has grown significantly over the last 30 years. In this article the authors present an overview of the clinical aspects, laboratory evaluation, and genetic defects of primary immunodeficiencies, with an emphasis on the pathophysiology of the known molecular defects. This article is designed to give the primary pediatrician a general knowledge of this rapidly expanding field.

X-linked susceptibility to mycobacteria is caused by mutations in NEMO impairing CD40-dependent IL-12 production

Germline mutations in five autosomal genes involved in interleukin (IL)-12-dependent, interferon (IFN)-gamma-mediated immunity cause Mendelian susceptibility to mycobacterial diseases (MSMD). The molecular basis of X-linked recessive (XR)-MSMD remains unknown. We report here mutations in the leucine zipper (LZ) domain of the NF-kappaB essential modulator (NEMO) gene in three unrelated kindreds with XR-MSMD. The mutant proteins were produced in normal amounts in blood and fibroblastic cells. However, the patients' monocytes presented an intrinsic defect in T cell-dependent IL-12 production, resulting in defective IFN-gamma secretion by T cells. IL-12 production was also impaired as the result of a specific defect in NEMO- and NF-kappaB/c-Rel-mediated CD40 signaling after the stimulation of monocytes and dendritic cells by CD40L-expressing T cells and fibroblasts, respectively. However, the CD40-dependent up-regulation of costimulatory molecules of dendritic cells and the proliferation and immunoglobulin class switch of B cells were normal. Moreover, the patients' blood and fibroblastic cells responded to other NF-kappaB activators, such as tumor necrosis factor-alpha, IL-1beta, and lipopolysaccharide. These two mutations in the NEMO LZ domain provide the first genetic etiology of XR-MSMD. They also demonstrate the importance of the T cell- and CD40L-triggered, CD40-, and NEMO/NF-kappaB/c-Rel-mediated induction of IL-12 by monocyte-derived cells for protective immunity to mycobacteria in humans.

Umbilical cord stem cell transplantation for primary immunodeficiencies

Primary immunodeficiencies (PIDs) are a rare but important cause of mortality and morbidity in childhood: the most severe--known as severe combined immunodeficiency (SCID)--are fatal within the first year of life; other PIDs are less immediately life-threatening, but have a poor long-term outlook. Haematopoietic stem cell transplantation (HSCT) is the best treatment for SCID and is increasingly offered for other PIDs. The best results are achieved with an HLA-matched family donor. Umbilical cord stem cells (UCSCs) are an alternative stem cell source. Results using UCSCs in the treatment of haematological disorders and malignancy are as good as those for which marrow is the stem cell source. Although PIDs make up a small proportion of disorders amenable to treatment by HSCT, UCSCs are an ideal source of haematopoietic stem cells for many of these patients. Of the 52 patients with SCID or other PIDs for whom detailed information on outcome is available, results of engraftment, immune reconstitution, incidence of graft-versus-host disease and survival are comparable with other stem cell sources. Small stem cell dose and prolonged time to viral immunity limit the patients for whom UCSCs can be used. Newer methods of achieving better engraftment, ex vivo expansion of stem cells and generation of antigen-specific cytotoxic T cells are being developed at present, and will widen the application of UCSCs as a viable source for more patients.

X-Linked Hyper-Immunoglobulin M Syndrome: Molecular Genetic Study and Long-Time Follow-Up of Three Generations of a Chinese Family

BACKGROUND

X-linked hyper-immunoglobulin M (IgM) syndrome (XHIGM) is a rare immunodeficiency disease caused by mutations of the CD40 ligand gene. Patients are subject to recurrent infections and have normal or elevated levels of IgM but markedly decreased serum IgG.

OBJECTIVE

We describe molecular genetic studies and clinical manifestations in three generations of one family, as well as results of long-term treatment of 2 young men with the disorder.

METHODS

Of 37 living family members, mutational analysis of the CD40 ligand gene was performed in 36 members. Laboratory data for patients and carriers were reviewed.

RESULTS

Four male family members had died of unexplained causes. The 3 patients with XHIGM syndrome and the 5 carriers all had a novel mutation located at Tyr 169 Asn (T526A) in exon 5, the tumor necrosis factor domain of the CD40 ligand gene. In the 3 patients, CD40 ligand expression in activated CD4+ T cells was below 1%. In the carriers, about half of activated CD4+ cells expressed CD40 ligand. One carrier had malignant lymphoma. Long-term (>20 years) intravenous immunoglobulin therapy in 2 patients improved IgG levels but did not fully suppress the high levels of IgM, nor did it prevent late complications (bronchiectasis and sclerosing cholangitis).

CONCLUSIONS

Diagnosis of a genetic immunodeficiency, especially an X-linked disease such as XHIGM syndrome, should prompt a survey of the entire family.

Host genetic factors and mycobacterial infections: lessons from single gene disorders affecting innate and adaptive immunity

This review summarizes the association of increased susceptibility to mycobacterial disease in patients with genetic defects affecting innate and adaptive immunity. The optimum function of CD4 T-cell and macrophage function is critically important for immunity against mycobacteria. Antibody, complement and neutrophil function is not required for effective anti-mycobacterial immunity.

CD154 Is Essential for Protective Immunity in ExperimentalSalmonellaInfection: Evidence for a Dual Role in Innate and Adaptive Immune Responses

CD40-CD154 interactions are of central importance in the induction of humoral and cellular immune responses. In the present study, CD154-deficient (CD154-/-) mice were used to assess the role of CD40-CD154 interactions in regulating the immune response to a systemic Salmonella infection. Compared with C57BL/6 (CD154+/+) controls, CD154-/- mice were hypersusceptible to infection by an attenuated strain of Salmonella enterica serovar Typhimurium (S. typhimurium), as evidenced by decreased survival rate and mean time to death, which correlated with increased bacterial burden and persistence in target organs. CD154-/- mice exhibited a defect both in the production of IL-12, IFN-gamma, and NO during the acute phase of the disease and in the generation of Salmonella-specific Ab responses and Ig isotype switching. Furthermore, when CD154-/- animals were administered a sublethal dose of attenuated S. typhimurium and subsequently challenged with a virulent homologous strain, all mice succumbed to an overwhelming infection. Similar treatment of CD154+/+ mice consistently resulted in > or =90% protection. The lack of protective immunity in CD154-/- mice correlated with a decreased T cell recall response to Salmonella Ags. Significant protection against virulent challenge was conferred to presensitized CD154-/- mice by transfer of serum or T cells from immunized CD154+/+ mice. For best protection, however, a combination of immune serum and T cells was required. We conclude that intercellular communications via the CD40-CD154 pathway play a critical role in the induction of type 1 cytokine responses, memory T cell generation, Ab formation, and protection against primary as well as secondary Salmonella infections.

Critical function of the CD40 pathway in parvovirus B19 infection revealed by a hypomorphic CD40 ligand mutation

Parvovirus B19-induced chronic anemia has been associated with failure to mount an effective neutralizing antibody response. We describe an adolescent male with a 13-year history of parvovirus B19-induced anemia as the primary manifestation of X-linked hyper IgM immunodeficiency (XHIM). This patient, whose serum IgG concentration was at the low end of the normal range and who mounted IgG antibody responses to T cell-dependent antigens, suffered from a nonsense mutation (R11 --> X) in the CD40 ligand (CD40L) gene. This resulted in low-level expression of a mutant CD40L predicted to lack the cytoplasmic domain. Intravenous immunoglobulin therapy alone or in combination with interferon gamma, given in the context of impaired Th1 cytokine production, suppressed but did not eradicate the infection. These results highlight the critical function of the CD40/CD40L pathway in parvovirus B19 infection and suggest that subtle defects in this pathway may underlie cases of chronic parvovirus B19 infection atypical of XHIM.

[Platelet-associated CD154: a new interface in haemostasis and in the inflammatory reaction]

Blood platelets play a crucial part in the blood clotting process by forming the platelet plug. Recent evidence indicates that they are likely to play a key role in the inflammatory reaction via CD154/CD40 interactions. CD40 was known to be widely expressed, for instance on cells of the vasculature including endothelial cells, smooth muscle cells and macrophages. It was also known that the triggering of CD40 on these cells led to the acquisition of an activated pro-inflammatory and pro-coagulant phenotype. It was subsequently shown that platelets express CD154 which is cryptic in unstimulated platelets but is expressed at the platelet surface upon platelet activation. When expressed at the platelet surface and exposed to CD40-expressing vascular cells, the platelet-associated CD154 triggers a variety of pro-inflammatory and pro-coagulant responses including induction of adhesion receptors, release of cytokines and chemokines, induction of tissue factor and of metalloproteinases. Platelet-associated CD154 is also involved in platelet/platelet interactions during platelet aggregation. Furthermore, in vivo models have emphasized the critical role of the platelet-associated CD154 in the progression of atherosclerotic disease and in the stabilization of arterial thrombi. Recent data show that CD40-bearing cells involved in fibrosis such as hepatic stellate cells and glomerular mesangial cells also respond to platelet-associated CD154, thus suggesting a new mechanism by which platelets may be instrumental in the inflammatory diseases of the liver or the kidney. Finally, platelet-associated CD154 has been shown to have immune competence both in vitro and in vivo, observations that open new fields of research on the potential implications of platelets in the immune response and auto-immune diseases.

Failure of HIV-exposed CD4+ T cells to activate dendritic cells is reversed by restoration of CD40/CD154 interactions

Because interactions between activated CD4+ T cells and antigen-presenting cells (APCs) are crucial for optimal APC function, defective CD4+ T-cell activation may contribute to APC dysregulation in HIV infection. Here, we show that CD4+ T cells exposed during stimulation to noninfectious HIV having functional envelope glycoproteins failed to provide activation signals to autologous dendritic cells (DCs). Consequently, important DC functions, including production of immunoregulatory cytokines (interleukin-12 p40 and interleukin-10) and up-regulation of costimulatory molecules (CD86, CD40, CD83), as well as the capacity to stimulate naive allogeneic T cells, were all adversely affected. The blunted up-regulation of CD154 in CD4+ T cells that were activated in the presence of noninfectious viruses is likely to be the major underlying mechanism for these defects. Addition of recombinant trimeric CD154 could restore production of cytokines by DCs cocultured with HIV-exposed T cells. Moreover, the functional defects mediated by coculture with HIV-exposed T cells were similar to those following antibody blockade of CD40-CD154 interactions. HIV-mediated blunted CD154 expression may thus play an important role in the suppression of cell-mediated immunity seen in HIV infection.

Syndrome de susceptibilite mendélienne aux infections mycobacteriennes : défauts de l’axe Interleukine-12 - Interféron

INTRODUCTION

Environmental non tuberculous mycobacteria and Bacillus Calmette-Guerin vaccines are weakly virulent mycobacteria. Nevertheless they may cause severe diseases in otherwise healthy children with no overt immunodeficiency. Parental consanguinity and familial forms are frequently observed among these patients, therefore this syndrome was named "Mendelian Susceptibility to Mycobacterial Disease".

STATE OF THE ART

In the last nine years, fife genes have been found to be mutated in patients with this syndrome: IFNGR1, IFNGR2, STAT1, IL12B, IL12RB1. Allelic heterogeneity accounts for ten distinct genetic disorders. Clinical phenotype differs between patients. The spectrum of disease extends from early-onset overwhelming mycobacterial infection to adult-onset localized disease and tuberculosis. Impaired IFN-gamma-mediated immunity is the common mechanism of the disease, outlining its major role in mycobacterial immunity.

PERSPECTIVES AND CONCLUSIONS

Better understanding of these disorders reveals an expanding clinical phenotype which justifies studying adult patients with pulmonary non tuberculous mycobacterial infection without known risk factors, severe BCGitis and recurrent tuberculosis. Molecular diagnosis makes it possible to introduce a specific regimen based on physiopathology.

Autoimmune retinopathy with RPE hypersensitivity and 'negative ERG' in X-linked hyper-IgM syndrome

PURPOSE

To report the clinical, electrophysiological, and immunological features of a patient with X-linked hyper-IgM immunodeficiency syndrome type 1 (HIGM1) accompanied by a novel type of autoimmune retinopathy, including retinal pigment epithelium (RPE) hypersensitivity.

METHODS

Comprehensive ophthalmological examinations, electrophysiological function testing, and inquiries into the immunological status of a 13-year-old presenting with subacute loss of vision in association with a molecularly confirmed diagnosis of HIGM1 were performed. The patient was genotyped by a PCR-based sequence tag content mapping strategy to define the genetic defect within the causative X-HIM gene TNFSF5. Since conventional allogenic bone marrow transplantation has been reported to cure HIGM1, a peripheral blood stem-cell transplantation was performed.

RESULTS

(1) The patient's reduced visual acuity included prolonged dark adaptation and visual field constriction. Electrophysiology revealed a 'negative ERG' indicating post-receptoral dysfunction. (2) Initial immunological examination of the patient's serum identified abnormal antibody activity with components of the photoreceptors and the inner nuclear layer. The patient later developed indications of RPE hypersensitivity. A massively reduced light-peak to dark-trough ratio of the EOG slow oscillations (L/D ratio) corresponded to impaired RPE-photoreceptor complex function. (3) Molecular genetic analyses revealed the patient to be nullizygous for the tumor necrosis factor ligand member 5 gene (TNFSF5; CD40LG). A large chromosomal deletion of approximately 27.6-32.3 kb in size was identified in Xq26. (4) The transplant with its associated immunomodulation appeared to worsen rather than improve the patient's condition.

CONCLUSIONS

The fundus appearance and electrophysiological function testing revealed indications of atypical retinal degeneration. However, the clinical course and the serological findings were consistent with those of ocular autoimmunity involving both antiretinal activity and RPE hypersensitivity. In this case, peripheral stem-cell transfusion with its associated chemotherapy failed to benefit the patient's vision; indications of autoimmunity appeared to increase following this treatment.

Cryptococcal meningitis in a patient with X-linked hyper-IgM1 syndrome

A case is reported of cryptococcal meningitis in a 27-y-old male suffering from X-linked hyper-IgM1 syndrome. This congenital disorder is characterized by multiple infections of the respiratory and gastrointestinal tracts, but also opportunistic infections commonly seen in patients with cell-mediated immunity. His clinical recovery was good but the need for life-long secondary chemoprophylaxis to prevent relapses is unknown.

Hyper-IgM1 syndrome with interstitial pneumonia and diarrhea caused by coxsackievirus B4 in a 3-month-old infant

BACKGROUND

Hyper-IgM1 syndrome is a rare genetic primary immunodeficiency disease caused by mutations of the CD40 ligand gene. It is characterized by normal or elevated levels of IgM and markedly decreased serum IgG, IgA, and IgE levels. Patients with this syndrome often easily develop infections. During the past decade, it has become clear that enteroviral infections may also occur as a manifestation of hyper-IgM1 syndrome.

OBJECTIVE

To report a case of hyper-IgM1 syndrome in a 3-month-old boy who had interstitial pneumonia and intractable diarrhea.

METHODS

Chest radiography, bronchoscopy, immune studies, and open lung biopsy were performed.

RESULTS

Chest radiography revealed diffuse bilateral infiltrates. Immune studies revealed the following proportions of lymphocyte markers: CD3, 5,976/microL; CD4, 5,015/microL; CD8, 866/microL; CD19, 1,325/microL; CD16 + 56, 935/microL; and active T cells, 225/microL. The IgG level was 190 mg/dL; IgA, 2 mg/dL; IgM, 34 mg/dL; IgE, 1 IU/dL; and CH50, 23.8/mL. CD40L expression was less than 1%, and a Tyr 169 Asn (t526a) mutation in the exon 5 tumor necrosis factor domain of the CD40L gene was found. The patient was treated with intravenous immunoglobulin and had a dramatic improvement in symptoms. Open lung biopsy failed to demonstrate pneumocystis, and there was no evidence of cryptosporidium in the stool. However, coxsackievirus B4 was isolated by viral throat culture.

CONCLUSION

Interstitial pneumonia and diarrhea caused by coxsackievirus B4 may be a complication of hyper-IgM1 syndrome.

B cells, E2A, and aging

Both mouse and human exhibit deficiencies in humoral immunity during 'old age'. While alterations in phenotype and function have been well documented, the molecular mechanisms that result in immune senescence remain undefined. B lymphopoiesis is suppressed in senescent mice, which may result from deficits at the pre-B-cell stage or earlier (e.g. pro-B cells). This deficit contrasts with the maintenance of the normal number of total peripheral B lymphocytes in senescent mice. However, mature peripheral B cells in aged mice can exhibit reduced efficiencies of both immunoglobulin isotype switching and somatic hypermutation. The basic helix-loop-helix transcription factor E2A is crucial at several stages of B-lymphocyte differentiation, including the development of pro-B and pre-B cells within the bone marrow and in isotype switch and somatic hypermutation among peripheral B cells. Therefore, we have focused on the regulation of E2A expression and function during both B lymphopoiesis and isotype class switching in senescent mice. These studies show that E2A expression is normally under complex control at both post-transcriptional and post-translational levels. Alterations in E2A expression at both the B-cell precursor and mature B-cell developmental stages are hypothesized to contribute to defects in humoral immunity during senescence.

Maintenance of the CD40-related immunodeficient response in hyper-IgM B cells immortalized with a LMP1-regulated mini-EBV

Our previous investigation of a patient (pt1) with non-X-linked hyper-immunoglobulin M syndrome revealed a CD40-mediated defect in B cell activation that resulted in low CD23 expression and absence of germ-line transcription and class-switch recombination. These deficiencies were complemented in vitro by a high threshold of sustained signaling through CD40. To further analyze the signaling defect in pt1 B cells, two types of Epstein-Barr virus lymphoblastoid cell lines (LCLs) were generated that either constitutively expressed the viral transforming protein latent membrane protein-1 (LMP1; pt1-LCL) or expressed it under the control of a tet-inducible promoter (pt1-LCL(tet)). Because LMP1 signals through the CD40 pathway, the pt1-LCL and pt1-LCL(tet) lines allow comparison of downstream functions in response to either constitutive LMP1 signals or regulated LMP1 and CD40 signals. Immortalized pt1-LCLs were initially CD23(lo)/CD38(hi) and reverted to a CD23(hi)/CD38(lo) phenotype upon extended growth in culture, suggesting that the CD40 defect was reversed by selection and/or constitutive expression of LMP1. In contrast, pt1-LCL(tet) cells retained the CD23(lo)/CD38(hi) phenotype after extended periods of culture and failed to up-regulate CD23 in response to CD40 signals. Analysis of pt1-LCL(tet) cells in response to the CD40 signals in the presence or absence of LMP1 revealed that mitogenic activation resulted only from LMP1 and not CD40, indicating a difference in the response of pt1 B cells to these two distinct signals. Together, these data demonstrate that the pt1-LCL(tet) cells maintain the CD40-related defect and provide a unique approach to study the independent effects of LMP1- and CD40-directed signals.

Congenital immunodeficiencies and sepsis

OBJECTIVE

Because a hallmark of congenital immunodeficiency disorders is susceptibility to recurrent, unusual and/or severe infections, an effort was undertaken to identify a subset of these patients with an increased risk for sepsis.

DESIGN

Literature review.

RESULTS

Twenty congenital immunodeficiency disorders were identified with increased sepsis susceptibility.

CONCLUSION

Distinguishing patients with congenital immunodeficiencies from others with sepsis has important implications for the future well-being of the immunodeficient patient because many of the diseases are modified favorably by appropriate treatment. In addition, better understanding of sepsis in the setting of congenital immunodeficiency has numerous implications for both immunodeficiency and sepsis research. As a group, these disorders define components of the human immune system that are essential for defense against severe infection and demonstrate immunologic themes underlying sepsis susceptibility.

Multi-dysfunctional pathophysiology in ITP

Idiopathic thrombocytopenic purpura (ITP) is an organ-specific autoimmune disorder characterized by a low platelet count and mucocutaneous bleeding. The decrease of platelets is caused by increased autoantibodies against self-antigens, particularly IgG antibodies against GPIIb/IIIa. The production of these autoantibodies by B cells depends on a number of cellular mechanisms that form a network of modulation, with T cells playing a pivotal role in pathophysiology. Delineation of the dysfunction of cellular immunity has recently been attempted. This review will focus on these recent advances applicable to ITP and to highlight how these may translate into novel approaches to treatment in the future. Multi-dysfunction in these networks may include a failure of self-antigen recognition and tolerance, involvement of abnormal cell surface molecules, altered Th1/Th2 cytokine profiles, impaired megakaryocytopoiesis and impaired cell-mediated cytotoxicity. In ITP, multi-step dysfunctions in these networks may take place that finally lead to the occurrence of the disease. Therefore, unveiling these dysfunctions is vital in understanding the pathophysiology of ITP and will finally lead to the development of new therapies to fight the disease.

A history of pediatric immunology

Immunology has played a prominent role in the history of medicine. Pediatric immunologists have focused on immune aberrations in pediatric disorders, particularly those involving host defense mechanisms. These efforts have paid rich dividends in terms of fundamental knowledge of the immune system and major therapeutic advances, including 1) i.v. immunoglobulin therapy, 2) hematopoietic stem cell transplantation, and 3) gene therapy. Pediatric immunology as an organized discipline emerged in the early 1950s, when pediatricians and their basic scientist colleagues began to focus on clinical and basic research related to immunodeficiency. Since then, key organizations and infrastructure have been developed to support this research and the clinical care of immunodeficient patients. We review here the evolution of contemporary pediatric immunology, particularly in North America, from its roots in 19th-century Europe to its current expression as one of the fundamental scientific and clinical disciplines of pediatrics.