Deficiency of adenosine deaminase 2 triggers adenosine-mediated NETosis and TNF production in patients with DADA2

Reduction of adenosine deaminase 2 (ADA2) activity due to autosomal-recessive loss-of-function mutations in the ADA2 gene (previously known as CECR1) results in a systemic vasculitis known as deficiency of ADA2 (DADA2). Neutrophils and a subset of neutrophils known as low-density granulocytes (LDGs) have been implicated in the pathogenesis of vasculitis, at least in part, through the formation of neutrophil extracellular traps (NETs). The study objective was to determine whether neutrophils and NETs play a pathogenic role in DADA2. In vivo evidence demonstrated NETs and macrophages in affected gastrointestinal tissue from patients with DADA2. An abundance of circulating LDGs prone to spontaneous NET formation was observed during active disease in DADA2 and were significantly reduced after remission induction by anti-tumor necrosis factor (TNF) therapy. Increased circulating LDGs were identified in unaffected family members with monoallelic ADA2 mutations. Adenosine triggered NET formation, particularly in neutrophils from female patients, by engaging A1 and A3 adenosine receptors (ARs) and through reactive oxygen species- and peptidylarginine deiminase-dependent pathways. Adenosine-induced NET formation was inhibited by recombinant ADA2, A1/A3 AR antagonists, or by an A2A agonist. M1 macrophages incubated with NETs derived from patients with DADA2 released significantly greater amounts of TNF-α. Treatment with an A2AAR agonist decreased nuclear translocation of NF-κB and subsequent production of inflammatory cytokines in DADA2 monocyte-derived macrophages. These results suggest that neutrophils may play a pathogenic role in DADA2. Modulation of adenosine-mediated NET formation may contribute a novel and directed therapeutic approach in the treatment of DADA2 and potentially other inflammatory diseases.

An essential role for the Zn2+ transporter ZIP7 in B cell development

Despite the known importance of zinc for human immunity, molecular insights into its roles have remained limited. Here we report a novel autosomal recessive disease characterized by absent B cells, agammaglobulinemia and early onset infections in five unrelated families. The immunodeficiency results from hypomorphic mutations of SLC39A7, which encodes the endoplasmic reticulum-to-cytoplasm zinc transporter ZIP7. Using CRISPR-Cas9 mutagenesis we have precisely modeled ZIP7 deficiency in mice. Homozygosity for a null allele caused embryonic death, but hypomorphic alleles reproduced the block in B cell development seen in patients. B cells from mutant mice exhibited a diminished concentration of cytoplasmic free zinc, increased phosphatase activity and decreased phosphorylation of signaling molecules downstream of the pre-B cell and B cell receptors. Our findings highlight a specific role for cytosolic Zn2+ in modulating B cell receptor signal strength and positive selection.

Ion channelopathies of the immune system

Ion channels and transporters move ions across membrane barriers and are essential for a host of cell functions in many organs. They conduct K+, Na+ and Cl-, which are essential for regulating the membrane potential, H+ to control intracellular and extracellular pH and divalent cations such as Ca2+, Mg2+ and Zn2+, which function as second messengers and cofactors for many proteins. Inherited channelopathies due to mutations in ion channels or their accessory proteins cause a variety of diseases in the nervous, cardiovascular and other tissues, but channelopathies that affect immune function are not as well studied. Mutations in ORAI1 and STIM1 genes that encode the Ca2+ release-activated Ca2+ (CRAC) channel in immune cells, the Mg2+ transporter MAGT1 and the Cl- channel LRRC8A all cause immunodeficiency with increased susceptibility to infection. Mutations in the Zn2+ transporters SLC39A4 (ZIP4) and SLC30A2 (ZnT2) result in nutritional Zn2+ deficiency and immune dysfunction. These channels, however, only represent a fraction of ion channels that regulate immunity as demonstrated by immune dysregulation in channel knockout mice. The immune system itself can cause acquired channelopathies that are associated with a variety of diseases of nervous, cardiovascular and endocrine systems resulting from autoantibodies binding to ion channels. These autoantibodies highlight the therapeutic potential of functional anti-ion channel antibodies that are being developed for the treatment of autoimmune, inflammatory and other diseases.

Dissecting Epigenetic Dysregulation of Primary Antibody Deficiencies

Primary antibody deficiencies (PADs), the most prevalent inherited primary immunodeficiencies (PIDs), are associated with a wide range of genetic alterations (both monogenic or polygenic) in B cell-specific genes. However, correlations between the genotype and clinical manifestations are not evident in all cases indicating that genetic interactions, environmental and epigenetic factors may have a role in PAD pathogenesis. The recent identification of key defects in DNA methylation in common variable immunodeficiency as well as the multiple evidences on the role of epigenetic control during B cell differentiation, activation and during antibody formation highlight the importance of investing research efforts in dissecting the participation of epigenetic defects in this group of diseases. This review focuses on the role of epigenetic control in B cell biology which can provide clues for the study of potential novel pathogenic defects involved in PADs.

A recurrent dominant negative E47 mutation causes agammaglobulinemia and BCR(-) B cells

Approximately 90% of patients with isolated agammaglobulinemia and failure of B cell development have mutations in genes required for signaling through the pre–B cell and B cell receptors. The nature of the gene defect in the majority of remaining patients is unknown. We recently identified 4 patients with agammaglobulinemia and markedly decreased numbers of peripheral B cells. The B cells that could be detected had an unusual phenotype characterized by the increased expression of CD19 but the absence of a B cell receptor. Genetic studies demonstrated that all 4 patients had the exact same de novo mutation in the broadly expressed transcription factor E47. The mutant protein (E555K) was stable in patient-derived EBV-transformed cell lines and cell lines transfected with expression vectors. E555K in the transfected cells localized normally to the nucleus and resulted in a dominant negative effect when bound to DNA as a homodimer with wild-type E47. Mutant E47 did permit DNA binding by a tissue-specific heterodimeric DNA-binding partner, myogenic differentiation 1 (MYOD). These findings document a mutational hot-spot in E47 and represent an autosomal dominant form of agammaglobulinemia. Further, they indicate that E47 plays a critical role in enforcing the block in development of B cell precursors that lack functional antigen receptors.

Efficient amyloid A clearance in the absence of immunoglobulins and complement factors

Amyloid A amyloidosis is a protein misfolding disease characterized by deposition of extracellular aggregates derived from the acute-phase reactant serum amyloid A protein. If untreated, amyloid A amyloidosis leads to irreversible damage of various organs, including the kidneys, liver, and heart. Amyloid A deposits regress upon reduction of serum amyloid A concentration, indicating that the amyloid can be efficiently cleared by natural mechanisms. Clearance was proposed to be mediated by humoral immune responses to amyloid. Here, we report that amyloid clearance in mice lacking complement factors 3 and 4 (C3C4(-/-)) was equally efficient as in wild-type mice (C57BL/6), and was only slightly delayed in agammaglobulinemic mice (J(H-/-)). Hence, antibodies or complement factors are not necessary for natural amyloid clearance, implying the existence of alternative physiological pathways for amyloid removal.

Pure red cell aplasia associated with Good's syndrome accompanied by decreased stem cell factor production in the bone marrow

A 79-year-old Japanese woman diagnosed with pure red cell aplasia (PRCA) associated with thymoma and hypogammaglobulinemia (Good's syndrome) was successfully treated with cyclosporine-A after a thymectomy. We further studied the etiology of this case. A burst-forming unit erythroid (BFU-E) assay with SCF restored erythropoiesis in vitro. SCF production was reduced in bone marrow stromal cells; however, it was restored in vitro and in vivo after cyclosporine-A treatment.

Clinical features and follow-up of Chinese patients with symptomatic hypogammaglobulinemia in infancy

BACKGROUND

Hypogammaglobulinemia is common in infant humoral immunodeficiencies and has complicated causes and outcomes. We aimed to determine the clinical manifestations, immunological changes and outcomes of Shanghai infants with hypogammaglobulinemia.

METHODS

Patients under 2 years old, having one or more warning signs of primary immunodeficiency disorders, serum immunoglobulin levels below the lower limit of reference range per age, and with normal numbers for lymphocyte subsets, were analyzed and followed up for 2 to 3 years.

RESULTS

A total of 91 children (male-to-female ratio: 2.25: 1) participated in the study. Initial clinical presentation was recurrent upper respiratory tract infection (46%), invasive infection (3%), atopic disease (32%). IgA reduction (77%) was prevalent; 34% patients had more than one isotype reduced. During follow-up, 51 of 62 patients (82.25%) had immunoglobulins normalized at the age between 12 - 48 months; these were diagnosed as transient hypogammaglobulinemia of infancy (THI). Long-term follow-up may reveal a diagnosis for the remaining 11 infants with persistent lower immunoglobulin levels, who did not have antibody titers measured. Earlier onset was correlated with higher rates of normalization. More patients were diagnosed with isolated hypogammaglobulinemia in 2006 compared with the previous 4 years (2002 - 2005).

CONCLUSIONS

The awareness of immunodeficiency among pediatricians has been greatly improved. Recurrent otitis media was not a major infection in our patients. THI is a relatively common condition associated with infant hypogammaglobulinemia. In the absence of specific antibody titers, the diagnosis of THI can be confirmed retrospectively with Ig levels normalized in follow-up visits. Therefore, long-term follow-up and frequent re-evaluation of these patients are necessary to distinguish them from true primary immunodeficiency.

Naturally occurring Bruton's tyrosine kinase mutations have no dominant negative effect in an X-linked agammaglobulinaemia cellular model

X-linked agammaglobulinaemia (XLA) is characterized by absence of mature B cells because of mutations in the Bruton's tyrosine kinase (Btk) gene. Btk-deficient early B cell precursors experience a block in their differentiation potentially reversible by the addition of an intact Btk gene. Btk expression was measured in 69 XLA patients with 47 different mutations and normal expression was detected in seven. We characterized these Btk mutant forms functionally by transfection into a lymphoma cell line that lacks endogenous Btk expression (Btk-/- DT40 cells) and analysed the calcium flux in response to B cell receptor stimulation. To test whether co-expression of a mutated form could compromise the function of the intact Btk transfection, studies in wild-type (WT) DT40 cells were also performed. Study reveals that none of the seven Btk mutants analysed was able to revert the absence of calcium mobilization upon IgM engagement in Btk-/- DT40 cells, as does intact Btk. In addition, calcium mobilization by anti-IgM stimulation in DT40 Btk+/+ cells was unaffected by co-expression with Btk mutants. These results suggest that gene addition would be feasible not only for patients with XLA and mutations that prevent Btk expression, but for those with expression of a mutant Btk.

Toll-like receptor signaling is impaired in dendritic cells from patients with X-linked agammaglobulinemia

Bruton's tyrosine kinase (BTK), which is defective in patients with X-linked agammaglobulinemia (XLA), is expressed not only in B cells but also in monocytes and dendritic cells (DCs). DCs play a crucial role in the innate immune response against infections by sensing pathogens through Toll-like receptors (TLRs). However, it is not known whether BTK deficiency in XLA might impair TLR-mediated signaling in DCs, which are susceptible to various infections. The phenotypic maturation and cytokine production mediated by TLRs were examined in monocyte-derived DC from XLA patients and normal controls. The TLR expression in DCs was analyzed by flow cytometry. TLR-mediated signaling in DCs was evaluated for the phenotypic maturation based on CD83 expression and production of cytokines, such as TNF-alpha, IL-6 and IL-12p70. TLR levels in DCs were similar between XLA and controls. TLR2, TLR4 and TLR7/8 ligands elicited less phenotypic maturation of DCs from XLA patients than normal controls based on CD83 expression. Stimulation with TLR2, TLR4 and TLR7/8 ligands, as well as TLR3 ligand, resulted in significantly lower production of TNF-alpha, but neither IL-6 nor IL-12p70, by DCs from XLA patients in comparison to normal controls. These findings suggest that BTK may thus be required for TLR signaling in DCs. The impaired TLR signaling in DCs may therefore be partly responsible for the occurrence of severe infections with bacteria and some viruses in XLA patients.

Severe FOXP3+ and naïve T lymphopenia in a non-IPEX form of autoimmune enteropathy combined with an immunodeficiency

BACKGROUND & AIMS

Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is the best-characterized form of a rare entity called autoimmune enteropathy (AIE). IPEX syndrome is due to mutations in the FOXP3 gene, a transcription factor essential for the development and function of the natural regulatory CD25(+)CD4(+) T cells. We studied a female patient with a polyautoimmune AIE syndrome resembling a mild form of IPEX syndrome but associated with recurrent bacterial infections and mild hypogammaglobulinemia. We hypothesized that this syndrome combined a deficit of FOXP3(+) cells and other lymphocyte populations.

METHODS

We analyzed the major lymphocyte subsets and the FOXP3(+) regulatory system in blood samples obtained during the 2-year period that followed the last autoimmune manifestation.

RESULTS

The patient had severe naïve T lymphopenia and a major deficit of FOXP3(+)CD4(+) T cells, both in circulation and in the highly inflamed intestinal mucosa, but mutations in the FOXP3 locus were excluded. The blood FOXP3(+) pool was devoid of CD25(high) cells, but the few regulatory CD25(+) cells were functional. Intrinsic defects in the expression of CD25, FOXP3, and interleukin 2 were excluded. Upon activation, a small subset of cells, presumably committed to regulatory function, sustained expression of CD25 and FOXP3.

CONCLUSIONS

Peripheral T lymphopenia of both naïve and natural regulatory T cells might be the consequence of defective thymic production or the short life span of exported T cells. This case sheds new light in the etiology of autoimmune manifestations in T-cell immunodeficiencies and in the heterogeneity of AIE.

Impaired Toll-like receptor 8–mediated IL-6 and TNF-α production in antigen-presenting cells from patients with X-linked agammaglobulinemia

The critical role of Bruton tyrosine kinase (Btk) in B cells has been documented by the block of B-cell development in X-linked agammaglobulinemia (XLA). Less is known about Btk function in myeloid cells. Several pieces of evidence indicate that Btk is a component of Toll-like receptor (TLR) signaling. We analyzed whether Btk deficiency in XLA is associated with an impaired dendritic cell (DC) compartment or defective TLR signaling. We analyzed the expression of TLRs 1 to 9 on myeloid DCs generated from XLA patients and evaluated their response to activation by specific TLR agonists. We show that XLA patients have normal numbers of circulating DCs. Btk-deficient DCs have no defect in response to stimulation of TLRs 1/2, 2/6, 3, 4, and 5 but display a profound impairment of IL-6 and TNF-α production in response to stimulation by TLR-8 cognate agonist, ssRNA. These findings may provide an explanation for the susceptibility to enteroviral infections in XLA patients.

WHIM syndrome: a defect in CXCR4 signaling

The study of inherited immunodeficiencies has proven valuable in elucidating molecular signaling cascades underlying the developmental and functional regulation of the human immune system. The first example of a human immunologic disease caused by mutation of a chemokine receptor was provided by WHIM (warts, hypogammaglobulinemia, infections, and myelokathexis) syndrome, a rare, combined immunodeficiency featuring an unusual form of neutropenia. Subsequent studies following the initial description of mutations in the CXCR4 gene have revealed a striking concordance in the types of mutations observed, suggesting that impaired regulation of receptor signaling by truncation of the cytoplasmic tail domain is an essential aspect in disease pathogenesis. Biochemical studies have provided support for the model that impaired receptor downregulation leads to the characteristic immunologic and hematologic disturbances. Interestingly, these genetic studies have also identified phenocopies with the same clinical features but without mutation of CXCR4, suggesting that mutations in as yet uncharacterized downstream regulators of the receptor may be involved in a proportion of cases.

Impaired humoral immunity in X-linked lymphoproliferative disease is associated with defective IL-10 production by CD4+ T cells

X-linked lymphoproliferative disease (XLP) is an often-fatal immunodeficiency characterized by hypogammaglobulinemia, fulminant infectious mononucleosis, and/or lymphoma. The genetic lesion in XLP, SH2D1A, encodes the adaptor protein SAP (signaling lymphocytic activation molecule-associated [SLAM-associated] protein); however, the mechanism(s) by which mutations in SH2D1A causes hypogammaglobulinemia is unknown. Our analysis of 14 XLP patients revealed normal B cell development but a marked reduction in the number of memory B cells. The few memory cells detected were IgM(+), revealing deficient isotype switching in vivo. However, XLP B cells underwent proliferation and differentiation in vitro as efficiently as control B cells, which indicates that the block in differentiation in vivo is B cell extrinsic. This possibility is supported by the finding that XLP CD4(+) T cells did not efficiently differentiate into IL-10(+) effector cells or provide optimal B cell help in vitro. Importantly, the B cell help provided by SAP-deficient CD4(+) T cells was improved by provision of exogenous IL-10 or ectopic expression of SAP, which resulted in increased IL-10 production by T cells. XLP CD4(+) T cells also failed to efficiently upregulate expression of inducible costimulator (ICOS), a potent inducer of IL-10 production by CD4(+) T cells. Thus, insufficient IL-10 production may contribute to hypogammaglobulinemia in XLP. This finding suggests new strategies for treating this immunodeficiency.

The B cell antigen receptor controls integrin activity through Btk and PLCgamma2

Integrin-mediated adhesion and B cell antigen receptor (BCR) signaling play a critical role in B cell development and function, including antigen-specific B cell differentiation. Here we show that the BCR controls integrin α4β1 (VLA-4)-mediated adhesion of B cells to vascular cell adhesion molecule-1 and fibronectin. Molecular dissection of the underlying signaling mechanism by a combined biochemical, pharmacological, and genetic approach demonstrates that this BCR-controlled integrin-mediated adhesion requires the (consecutive) activation of Lyn, Syk, phosphatidylinositol 3-kinase, Bruton's tyrosine kinase (Btk), phospholipase C (PLC)γ2, IP3R-mediated Ca²⁺ release, and PKC. In contrast, activation of mitogen-activated protein kinase kinase (MEK) or extracellular signal–regulated kinase (ERK) is not required, and simultaneous activation of MEK, ERK, and PKB is not sufficient either. Furthermore, Btk is also involved in the control of integrin-mediated adhesion of preB cells. The control of integrin α4β1-mediated B cell adhesion by the BCR involves cytoskeletal reorganization and integrin clustering. These results reveal a novel function for the BCR and Btk, i.e., regulation of integrin α4β1 activity, thereby providing new insights into the control of B cell development and differentiation, as well as into the pathogenesis of the immunodeficiency disease X-linked agammaglobulineamia (XLA).

Bruton's tyrosine kinase is required for lipopolysaccharide-induced tumor necrosis factor alpha production

Lipopolysaccharide (LPS), a product of Gram-negative bacteria, is potent mediator of tumor necrosis factor (TNF)alpha production by myeloid/macrophage cells. Inhibitors capable of blocking the signaling events that result in TNF alpha production could provide useful therapeutics for treating septic shock and other inflammatory diseases. Broad spectrum tyrosine inhibitors are known to inhibit TNF alpha production, however, no particular family of tyrosine kinases has been shown to be essential for this process. Here we show that the Bruton's tyrosine kinase (Btk)-deficient mononuclear cells from X-linked agammaglobulinemia patients have impaired LPS-induced TNF alpha production and that LPS rapidly induces Btk kinase activity in normal monocytes. In addition, adenoviral overexpression of Btk in normal human monocytes enhanced TNF alpha production. We examined the role of Btk in TNF alpha production using luciferase reporter adenoviral constructs and have established that overexpression of Btk results in the stabilization of TNF alpha mRNA via the 3' untranslated region. Stimulation with LPS also induced the activation of related tyrosine kinase, Tec, suggesting that the Tec family kinases are important components for LPS-induced TNF alpha production. This study provides the first clear evidence that tyrosine kinases of the Tec family, in particular Btk, are key elements of LPS-induced TNF alpha production and consequently may provide valuable therapeutic targets for intervention in inflammatory conditions.

Diagnosis of X-linked lymphoproliferative disease by analysis of SLAM-associated protein expression

X-linked lymphoproliferative disease (XLP) is an inherited immunodeficiency in which affected boys show abnormal responses to Epstein-Barr virus infection. The gene defective in XLP has been identified and designated SH2D1A and encodes a protein termed SLAM-associated protein (SAP). Mutation analysis in individuals with typical XLP presentations and family histories has only detected abnormalities in approximately 60% of patients. Thus, genetic analysis alone cannot confirm a diagnosis of XLP We have developed a SAP expression assay that can be used as a diagnostic indicator of XLP We show that SAP is constitutively expressed in normal individuals, in patients with severe sepsis and in patients with other primary immunodeficiencies. In six XLP patients, four with classical and two with atypical presentations, SAP expression was absent. In the latter two, who were previously assigned as having common variable immunodeficiency (CVID), the diagnosis of XLP was initially made using the protein expression assay. In two further patients in whom no mutation could be detected by genetic analysis, lack of SAP expression strongly suggests that these individuals have XLP. We therefore suggest that XLP should be suspected in certain boys previously diagnosed as having CVID and recommend that patients are investigated both by genetic analysis of SH2D1A and by expression of SAP protein.

Bruton's tyrosine kinase is required for activation of IkappaB kinase and nuclear factor kappaB in response to B cell receptor engagement

Mutations in the gene encoding Bruton's tyrosine kinase (btk) cause the B cell deficiency diseases X-linked agammaglobulinemia (XLA) in humans and X-linked immunodeficiency (xid) in mice. In vivo and in vitro studies indicate that the BTK protein is essential for B cell survival, cell cycle progression, and proliferation in response to B cell antigen receptor (BCR) stimulation. BCR stimulation leads to the activation of transcription factor nuclear factor (NF)-kappaB, which in turn regulates genes controlling B cell growth. We now demonstrate that a null mutation in btk known to cause the xid phenotype prevents BCR-induced activation of NF-kappaB. This defect can be rescued by reconstitution with wild-type BTK. This mutation also interferes with BCR-directed activation of IkappaB kinase (IKK), which normally targets the NF-kappaB inhibitor IkappaBalpha for degradation. Taken together, these findings indicate that BTK couples IKK and NF-kappaB to the BCR. Interference with this coupling mechanism may contribute to the B cell deficiencies observed in XLA and xid.

Impaired Ca2+ mobilization by X-linked agammaglobulinaemia (XLA) B cells in response to ligation of the B cell receptor (BCR)

XLA bone marrow samples were shown to contain B cells expressing IgM, and pre-B cells that express the mu-surrogate light chain (mu psiLC) complex, albeit at a reduced frequency to that found in normal bone marrow. Antibody ligation of mu heavy chain on these cells and an XLA B cell line did not induce a Ca2+ flux, whereas ligation of mu heavy chain on normal bone marrow cells, mu psiLC+ pre-B cell lines and an IgM+ B cell line did. The block in XLA B cells was not due to a defect in the basic mechanism of Ca2+ flux generation, as the cells responded well to thapsigargin. In addition, the defect did not affect T cells, which were shown to respond to CD3 antibody with a Ca2+ flux. Ligation of mu heavy chain on XLA bone marrow cells did, however, activate tyrosine kinases, resulting in tyrosine phosphorylation of a cellular protein with a molecular weight of approximately 115 kD. These results indicate that Btk may be necessary for the generation of the Ca2+ flux in response to ligation of mu heavy chain on B cells and mu psiLC+ pre-B.

Cytokine production in transient hypogammaglobulinemia and isolated IgA deficiency

BACKGROUND

Transient hypogammaglobulinemia of infancy and isolated IgA deficiency are characterized by normal numbers of circulating B lymphocytes. It is likely that no single abnormality, but rather different factors, may be relevant for the delayed onset of IgG synthesis in transient hypogammaglobulinemia or for the differentiation defect of B cells in IgA deficiency. These factors may include defective production of cytokines or an abnormal response of B cells to various mediators. Alternatively, some cytokines may act as inhibitory factors of B-cell function.

METHODS

The ability of peripheral blood mononuclear cells from children with proved or probable transient hypogammaglobulinemia (30 patients) and IgA deficiency (15 patients) to secrete several cytokines on stimulation with phytohemagglutinin in vitro was analyzed.

RESULTS

An enhanced production of tumor necrosis factor (TNF)-alpha, TNF-beta, and IL-10 was observed in transient hypogammaglobulinemia; whereas secretion of IL-1, IL-4, and IL-6 was essentially similar in the control and patient groups. Increased frequency of mononuclear cells secreting TNF-alpha was seen in the patient groups. Apart from elevated production of TNF-alpha, no other abnormalities in cytokine synthesis in selective IgA deficiency were observed. In vitro observations showed that exogenously added TNF-alpha and TNF-beta inhibited IgG and IgA secretion by pokeweed mitogen-stimulated mononuclear cells. During follow-up of 10 children, normalization of serum IgG level was associated with a decrease in previously elevated TNF-alpha and TNF-beta production, but IL-10 production remained unchanged.

CONCLUSION

These results suggest that TNF may be involved in the regulation of IgG and IgA production and can be associated with an arrest of IgG and IgA switch of B cells in hypogammaglobulinemia. The balance between TNF and IL-10 may be important for the normal development of IgG-secreting B cells.

Structure of the PH domain and Btk motif from Bruton's tyrosine kinase: molecular explanations for X-linked agammaglobulinaemia

Bruton's tyrosine kinase (Btk) is an enzyme which is involved in maturation of B cells. It is a target for mutations causing X-linked agammaglobulinaemia (XLA) in man. We have determined the structure of the N-terminal part of Btk by X-ray crystallography at 1.6 A resolution. This part of the kinase contains a pleckstrin homology (PH) domain and a Btk motif. The structure of the PH domain is similar to those published previously: a seven-stranded bent beta-sheet with a C-terminal alpha-helix. Individual point mutations within the Btk PH domain which cause XLA can be classified as either structural or functional in the light of the three-dimensional structure and biochemical data. All functional mutations cluster into the positively charged end of the molecule around the predicted binding site for phosphatidylinositol lipids. It is likely that these mutations inactivate the Btk pathway in cell signalling by reducing its affinity for inositol phosphates, which causes a failure in translocation of the kinase to the cell membrane. A small number of signalling proteins contain a Btk motif that always follows a PH domain in the sequence. This small module has a novel fold which is held together by a zinc ion bound by three conserved cysteines and a histidine. The Btk motif packs against the second half of the beta-sheet of the PH domain, forming a close contact with it. Our structure opens up new ways to study the role of the PH domain and Btk motif in the cellular function of Btk and the molecular basis of its dysfunction in XLA patients.

Epstein-Barr virus (EBV)-induced CD30+ natural killer cell-type malignancy resembling malignant histiocytosis: malignant transformation in chronic active EBV infection associating hypogammaglobulinemia

A 27-year-old male suffered from Epstein-Barr virus (EBV)-related liver dysfunction with persistent hypogammaglobulinemia. IgG titers to EBV antigens were significantly high, while other hepatitis markers were negative. Liver biopsy disclosed active intralobular inflammation. Two years later, he manifested persistent fever, leukopenia, effusions and hypoproteinemia, and his general condition worsened progressively. The peripheral blood small lymphocytes predominantly expressed natural killer (NK)-like phenotypes (CD2+, CD7+, CD16+, CD56+). Hepatosplenomegaly and marked elevation of serum lactic dehydrogenase were observed. He died of respiratory failure at the age of 29. At autopsy, the liver (2190 g), spleen (860 g), small bowel and mesenteric lymph nodes showed massive infiltration of large atypical lymphoid cells in close association with hemophagocytic histiocytes. Involvement was mildly noted also in the bone marrow, lungs, gall-bladder and kidneys. The atypical cells belonged to CD30+ activated NK-type cells expressing CD2, cytoplasmic CD3 epsilon, CD7, CD45RO, CD56, HLA-DR and HLA-DQ. T cell receptors (TCR), surface CD3, CD4, CD5 and CD8 were not expressed. Epstein-Barr virus-related small nuclear RNA (EBER1) and Epstein-Barr virus-associated nuclear antigen 1 were detected in the nuclei of a significant number of atypical cells, while EBV-related latent membrane protein-1 was negative. EBER1 was also identified in the nuclei of non-neoplastic small lymphocytes at both biopsy and autopsy. Monoclonal integration of the EBV genome into the lymphoma cells was shown by Southern blot analysis. Clonal rearrangement of TCR was undetectable. Roles of chronic active EBV infection in the development of NK cell-type malignancy resembling malignant histiocytosis are discussed.

Therapeutic application of intravenous human natural immunoglobulin preparation

Human natural immunoglobulin (HunIg) preparation for intravenous use has been used in various diseases. The most typical application of this preparation is agammaglobulinemia. Currently, however, this preparation is being used in the therapy of many other disorders. These include thrombocytopenia, Kawasaki disease, systemic vasculitis, several other disorders of autoimmune origin and systemic inflammation such as sepsis. In some diseases, the clinical improvement following use of HunIg has been dramatic, while in others its effect is not striking. Due to rarity of the side effects, the range of application of HunIg has been recently broadened. Such side effects include transmission of several diseases such as hepatitis and retroviral infections. Before it is recommended for use, however, and primarily due to expense, the efficacy of this drug should be carefully evaluated. The mechanism of action of HunIg is not fully understood. However, it has been suggested that its action may involve blockade of Fc-receptor, an anti-cytokine effect, or inhibition of complement activation. In this review, the mechanism of action of HunIgG and its application in human diseases are discussed.

Molecular genetic analysis of X-linked hypogammaglobulinemia and isolated growth hormone deficiency

In 1980 the clinical syndrome of X-linked hypogammaglobulinemia and isolated growth hormone deficiency (XLA/GHD) was described. XLA/GHD patients have reduced serum levels of Ig and normal cell-mediated immunity, and thus resemble patients with Bruton's X-linked agammaglobulinemia (XLA). However, XLA/GHD patients also have isolated GHD. Mutations and deletions in the Bruton's tyrosine kinase gene (BTK) are responsible for Bruton's XLA. We investigated BTK gene expression in an XLA/GHD patient from the family originally described by Northern analysis, cDNA sequencing, and Western analysis of protein production using mAb to BTK. BTK mRNA was normal in size and abundance, and the mRNA sequence was normal over the coding region, except for a single silent mutation. BTK protein was present in normal amounts in PBMC of this patient. Thus, at the molecular level, XLA/GHD is a different disease entity from Bruton's XLA. These results suggest that undescribed genes critical for B cell development and growth hormone production exist on the X chromosome.

Immunofluorescence analysis of IgA binding by human mononuclear cells in blood and lymphoid tissue

The nature of IgA-binding cells and their tissue distribution was examined by an indirect immunofluorescence assay with the use of IgA1 and IgA2 paraproteins and fluorochrome- or biotin-labeled F(ab')2 fragments of idiotype-specific antibodies. The frequency of IgA-binding mononuclear cells was approximately 13% in blood and spleen samples but less than 1% in tonsil samples. IgA binding could be visualized by flow immunocytometry on monocyte/macrophages, but not on T and B cells. IgA polymers were bound better than IgA dimers and monomers. Nonhomologous IgA myelomas of both IgA1 and IgA2 subclasses inhibited the IgA-binding to monocytes, whereas aggregated normal serum IgG, IgM paraproteins, and an IgG myeloma did not. IgA binding was relatively insensitive to changes in temperature or cation concentration. IgA-binding monocytes were found in IgA-deficient patients at the same frequency as in normal individuals. The results indicate that monocytes constitutively express class-specific binding sites for both IgA1 and IgA2 molecules.

Jejunal mucosal enzyme activities, regulatory peptides and organelle pathology of the enteropathy of common variable immunodeficiency

Jejunal biopsies from six patients having the small bowel enteropathy associated with common variable immunodeficiency have been subjected to analytical subcellular fractionation and enzymic and regulatory peptide microassay to define the organelle pathology of this syndrome. Compared with normal subjects, the immunodeficient patients had decreased activities of the three brush border enzymes: alkaline phosphatase, gamma-glutamyl transferase and alpha-glucosidase. The other organelle marker enzyme activities and all the regulatory peptide concentrations did not differ from the controls. Density gradient experiments showed a complete loss of particulate beta-glucosidase (lactase) with activity entirely located in the cytosol. The integrity of other organelles was normal. These data indicate that the enteropathy of common variable immunodeficiency is associated with abnormalities in the jejunal brush border analogous to those present in tropical malabsorption syndrome.

Kinetics of the spontaneously occurring common variable hypogammaglobulinemia: an analysis of two individuals with previously normal immunoglobulin levels

Two males with previously normal serum immunoglobulin levels who spontaneously developed common variable hypogammaglobulinemia were investigated. In one patient serum samples obtained before and after the development of hypogammaglobulinemia were analyzed. A parallel decrease in serum IgM, IgG (all 4 subclasses), IgA (both subclasses) as well as kappa and lambda light chains was found. Serum IgD and IgE also decreased but reached a minimum level before the other immunoglobulin classes. A bone marrow aspirate obtained before the development of hypogammaglobulinemia in this patient showed 1.2% plasma cells, whereas the frequency was only 0.1% when low serum immunoglobulins were recorded. These observations demonstrate the existence of adult onset hypogammaglobulinemia.

Microbial and metabolic profile of achlorhydric stomach: comparison of pernicious anaemia and hypogammaglobulinaemia

The microbial flora and some of its metabolites and enzymes in the stomach were compared in patients with achlorhydria, pernicious anaemia, and primary hypogammaglobulinaemia and in patients with dyspepsia with normal gastric acidity. Detailed analysis of the flora of the gastric juice and of the mucosa from the antrum, body, and fundus in six patients with hypogammaglobulinaemia (mean pH 8.2), seven patients with pernicious anaemia (mean pH 7.3), and five patients with dyspepsia (mean pH 1.9) yielded 22 different genera of bacteria, mainly from the patients with achlorhydria, the most common being streptococci, micrococci, staphylococci, veillonella, and lactobacilli. A similar flora was found associated with the mucosa at all three sites. Various metabolites were also looked for. beta Glucoronidase and C14 lipase were found in patients with hypogammaglobulinaemia but not in those with pernicious anaemia or dyspepsia. Volatile fatty acids were not found. Relatively high concentrations of ethanol were found in the patients with hypogammaglobulinaemia compared with those with pernicious anaemia (p = 0.02). Similar concentrations of dimethylamine were found in all three groups, but the concentrations of trimethylamine were much higher in patients with pernicious anaemia and hypogammaglobulinaemia. The high concentrations of some microbial enzymes and ethanol differentiated the group with hypogammaglobulinaemia from the rest, and these may bear some relation to the high incidence of gastric cancer in patients with hypogammaglobulinaemia.

Metabolic defects in immunodeficiency diseases

There are two ways to find the cause of primary immunodeficiency diseases. One approach is to start with the immune defect and work backwards, using in vitro techniques to define where the primary abnormality lies in the immune response. Immunologists favour this approach for obvious reasons; and it is not without virtue since, for example, it has shown that the defect in most cases of primary hypogammaglobulinaemia is due to a failure of B lymphocyte maturation. The alternative approach is to screen empirically for defects in biochemical pathways in the hope of finding a clue which will eventually lead to the underlying disorder. This is a sensible approach in diseases which are clearly inherited (e.g. X-linked hypogammaglobulinaemia) but is less attractive in a disease such as late onset hypogammaglobulinaemia which is not obviously inherited. In practice, such procedures involve screening the urine for abnormalities in the quality or quantity of excreted compounds. Another way is to screen for abnormalities in organelle integrity by measuring the activity of various enzymes in subcellular fractions. In reality, the clue to the metabolic defect is usually discovered by accident, the prime example in our field being the discovery of adenosine deaminase (ADA) deficiency.

beta 2-Microglobulin in saliva and its relation to flow rate in different glands in man

The concentration of beta 2-microglobulin (beta 2-m) in parotid saliva and sera from 13 adult hypogammaglobulinaemic subjects and in parotid saliva from 7 normal adults was determined by radioimmunoassay. Parotid and submandibular/sublingual saliva was collected from four normal and one hypogammaglobulinaemic subject in unstimulated and stimulated samples, and concentrations of IgA and beta 2-m were determined. The beta 2-m concentration in parotid saliva from hypogammaglobulinaemic subjects was 0.50 mg/l (0.2-1.1) and in normal adults 0.41 mg/l (0.2-0.9). In parotid saliva, the concentration of beta 2-m was negatively correlated with the flow rate, whereas in submandibular/sublingual a positive correlation was seen. Serum levels of beta 2-m in hypogammaglobulinaemic subjects were within the normal range of healthy adults. Gel filtration of saliva separated beta 2-m from IgA and from high molecular weight agglutinins. Beta 2-m was eluted as one single peak.

Increased adenine nucleotide turnover in duchenne muscular dystrophy

To investigate a possible disorder of adenine nucleotide turnover in Duchenne muscular dystrophy, we evaluated 15 patients with mild Duchenne muscular dystrophy, eight patients with severe muscular dystrophy, seven patients with other neuromuscular disorders, and eight patients with hypogammaglobulinemia but no muscle disease. The serum urate concentration was similar in all four groups. Base line urinary purine excretion was elevated in all patients with neuromuscular disease with values of 1.72 +/- 0.15, 2.37 +/- 0.22, 2.49 +/- 0.35, and 2.60 +/- 0.48 mumoles/100 ml glomerular filtration for control subjects, mild Duchenne muscular dystrophy, severe disease, and other neuromuscular diseases, respectively. Adenine nucleotide pool turnover was measured by labeling with [8-14C]adenine and then 5 days later administering intravenous fructose. Five-day cumulative mean radioactivity excretion was elevated in mild and severe Duchenne muscular dystrophy with excretion values of 11.4 +/- 0.7 and 11.5 +/- 1.1% of administered radioactivity, respectively, as compared to 9.0 +/- 0.9% of administered radioactivity for control subjects. After intravenous fructose infusion, patients with Duchenne muscular dystrophy had a less than normal rise in serum urate concentration, a normal increase of urinary urinary purine excretion, and a greater than normal elevation of urinary radioactivity excretion and urinary purine specific activity. Patients with other neuromuscular diseases had virtually no rise in plasma urate concentration, less than normal increase in urinary total purine excretion, and a greater than normal increase of urinary radioactivity excretion and urinary specific activity. These observations suggest that there is an increased rate of adenine nucleotide turnover in Duchenne muscular dystrophy. In patients with other neuromuscular disease an increased rate of adenine nucleotide turnover resembled the abnormality expected from a diminished adenine nucleotide pool.

An immunodeficient child with inflammatory bowel disease: involvement of cyclic nucleotides and effects of lithium

A 3-year-old male with inflammatory bowel disease and hypogammaglobulinemia was found to have decreased T lymphocyte function. His serum was shown to depress normal T cell proliferative responses to phytohemagglutinin. Incorporation of lithium chloride to in vitro cultures enhanced autologous lymphocyte responses to phytohemagglutinin. Since lithium acts by inhibiting cAMP production, the child's lymphocytes were postulated to have increased levels of cAMP. Both lymphocytes and serum were shown to contain elevated levels of cAMP. In vivo therapy with lithium citrate was initiated and enhanced T cell numbers and function were observed concomitantly. Serum cAMP was also reduced to normal levels. The patient showed initially marked clinical improvement as assessed by mood, weight gain, and diminution of diarrhea. This clinical improvement was unfortunately not sustained despite the continued improvement in immune parameters and cAMP levels.

Colostral immunoglobulin transfer in calves. III. Amount of absorption

Amount of colostrum fed and age at first feeding are the two major factors in determining maximum immunoglobulin concentration in serum for each immunoglobulin class in postcolostral calves. Both factors show linear response: increasing age, decreasing concentration; increasing amount fed up to 2 liters, increasing concentration. The two factors interact in a curvilinear response. Calves with initial feeding at progressively older ages need less colostrum to reach maximum absorption. Maximum absorption is represented by a progressively lower immunoglobulin concentration in serum with increasing age. Response surface contours for the maximum immunoglobulins IgG, IgM, and IgA, based on experimental data, have been included. Neither body weights of the experimental calves nor pooled colostral concentrations of immunoglobulin from pooled colostrums fed to the calves influenced maximum concentrations of immunoglobulin in serum.

Viral protein sythesis by tissues from avian leukosis virus-infected chickens. II. Effect of passive neutralizing antibody in normal and agammaglobulinaemic chickens

Synthesis in vitro of avian leukosis virus (ALV) group (gs proteins, p27 and p12, by various tissues from chickens infected within a few days after hatching was studied by means of autoradiography of immunoelectrophoretic patterns. Viral protein was synthesized in all tissues of chicks examined between days 18 and 50 of age after which time liver, kidney, bursa, thymus, and spleen became negative. The lung and genital organs of the chicks, however, continued to synthesize viral protein up to 100 days of age, when the experiment was ended. Repeated injections of neutralizing chicken antibody to ALV (Ab) starting on day 26 or 37 caused gs protein to decrease in spleen, liver, and thymus within 5 days but not in bursa, lung, and genital organs. Agammaglobulinaemic (Agamma) chickens showed prolonged persistence of gs protein synthesis in the spleen and liver; this synthesis was abrogated by passive Ab. Liver from Agamma chickens, however, also became negative without Ab treatment. The relative roles of antibody and cellular immunity in influencing ALV replication during the initial phase of infection before lymphoma development are discussed.

Protein A-positive staphylococci serve as a selective B cell mitogen for lymphocytes from primary immunodeficiency patients

Staphylococcus aureus protein A-positive bacteria have recently been proposed as selective B lymphocyte mitogens. We have studied the lymphocyte response to such mitogens in bacteria in normal subjects and in patients with primary immunodeficiencies. Patients with primary T cell defects show a normal response to protein A-positive bacteria and impaired responses to PHA and Con A. In contrast, patients with Bruton agammaglobulinaemia respond normally to these T cell mitogens but not to the bacteria. Thus, protein A-positive bacteria fulfil the criteria for being a T cell-independent B cell mitogen for human peripheral blood cells.

Protein synthesis and secretion by activated human lymphocytes

Human peripheral blood mononuclear cells showed increased synthesis and secretion of protein in response to stimulation by mitogens. Protein secretion in response to concanavalin A (Con A) correlated with cellular proliferation and originated from the proliferating cells. Selective depletion of either B lymphocytes or monocytes did not lead to a reduction in the total protein secreted, suggesting that the T lymphocyte was the cell contributing most of the synthetic activity. It is concluded that the measurement of newly synthesized and secreted protein by Con A activated mononuclear cells is a measurement of the T-lymphocyte response.

Intra- and extravascular distribution of albumin and immunoglobulin in man

The plasma proteins are constantly shuttling between intravascular and extravascular mass of a specific plasma protein is determined by its individual rate of synthesis and the mean total time it spends in plasma. The ratio of intravascular to total mass (distribution ratio) is determined by the relative rate, at which it passes from plasma to interstitial spaces (transcapillary escape rate: TER) and the relative return rate via lymph. TER in a specific organ depends on the local leakiness of the microvasculature. The overall value in normal man varies with the molecular weight of the protein being about 5%/h of the intravascular albumin mass, 3%/h for IgG and less than 1%/h for IgM. The higher the TER, the lower is the intravascular fraction. Hypertension, diabetes mellitus, burns, myxedema and certain types of liver cirrhosis will increase TER. In hypertension and diabetes this may be compensated for by an increased lymphatic return rate. Hypoproteinemia due to malnutrition or urinary or gastrointestinal loss is accompanied by a shift from the extravascular to the intravascular space.

Free immunoglobulin light chain synthesis by lymphocytes from patients with hypogammaglobulinaemia

Lymphocytes from six individuals with reduced or deficient serum immunoglobulins of one or more class were assessed for immunoglobulin production in vitro. There was no clinical evidence of a secondary cause for hypogammaglobulinaemia and three of the cases were receiving immunoglobulin therapy. The predominant immunoglobulin product in the culture supernatants form four cases was free light chain. In contrast, peripheral lymphocytes from two cases with partial IgA deficiency and from normal individuals exhibited a balanced synthesis of heavy and light chains. These findings are discussed with particular reference to free light chain synthesis by immature neoplastic B lymphocytes and to normal B lymphocyte differentiation.

[Agammaglobulinemia and secretory IgA (author's transl)]

After serum IgA has been intravenously administered, it appears immediately in secretions, sputum, and urine. At about the same time, a mechanism is employed which leads to the concentration of IgA in the sputum. In urine, 7sIgA and SC were separately eliminated; a linkage with 11sIgA did not occur. Similar relationships are probably present in the sputum, but exact proof could not be provided. By administrating immunoglobulin concentrates which contain IgA in 7s-serum form, the IgA concentration in external secretions can be raised; replacing the physiological 11s-IgA however, is not possible. The extent to which 7sIgA can take over the function of 11sIgA in these secretions has not yet been clarified. In this connection, the use of local 11sIgA inhalation therapy rather than ultrasound atomazation seems to be well founded theoretically and also promising. Whether such therapy can be carried out practically and is successful remains to be seen.

Synthesis of immunoglobulin and secretory component by gastrointestinal mucosa in patients with hypogammaglobulinaemia or IgA deficiency

Biopsies of intestinal mucosa from patients with adult hypogammaglobulinaemia or selective IgA deficiency have been studied for the ability to synthesize immunoglobulins and secretory component. Tissue fragments were cultured in vitro in medium containing 14C-labelled amino acids and newly snythesized proteins were detected by radioimmunoelectrophoresis. Synthesis of IgA, and in some cases IgG and IgM, was found in intestinal mucosal biopsies from hypogammaglobulinaemics and IgA-deficient subjects. Biopsies from all the patients also synthesized secretory component, but evidence was obtained which indicated that secretory component does not combine normally with IgA. Tissue sections of these biopsies have also been studied by immunofluorescence and immunoglobulin bearing cells have been demonstrated. The present findings demonstrate that immunoglobulin synthesizing cells are present in the intestinal mucosa of immunoglobulin-deficient individuals. Local immunoglobulin synthesis may partially explain why these patients do not often have major problems with intestinal infections.

Failure of heavy chain glycosylation of IgG in some patients with common, variable agammaglobulinemia

Four patients with common, variable agammaglobulinemia were preveiously reported to have normal numbers of circulating B lymphocytes which synthesized normal amounts of IgG in tissue culture but failed to secrete the newly synthesized IgG. The B lymphocytes of these patients fail to incorporate [3H]mannose and/or [3H]glucosamine into newly synthesized IgG, whereas such incorporation appears to occur just before IgG secretion in cultures of normal B lymphocytes.

Antigen binding by non-bursa-derived chicken leukocytes

Antigen-binding peripheral blood leukocytes (PBL) from normal and bursectomized agammaglobulinemic chickens were labeled by incubation in vitro with radioiodinated antigen at 4 degrees C in the presence of sodium azide. [125I]TGAL-binding cells could be detected by autoradiography of PBL from normal, unimmunized chickens at a frequency of 1 to 4 labeled cells per 10(4) leukocytes. No [125I]TGAL-binding cells were found in PBL from bursectomized chickens, even after incubation with 25 mug/ml of labeled antigen followed by prolonged autoradiographic exposure. The binding to normal PBL was specific as judged by inhibition with unlabeled TGAL but not with unlabeled TIGAL. The binding was, furthermore, inhibited by preincubation with rabbit anti-chicken L chain antibody but unaffected by normal rabbit IgG. [125I]TIGAL was, in contrast, found to bind to PBL from both normal and bursectomized chickens at a frequency of 6 to 80 labeled cells per 10(4) leukocytes. The labeling was specific, since it was inhibited by cold TIGAL but not by cold TGAL. The binding of [125I]TIGAL to PBL from bursectomized chickens showed from none to slight inhibition on preincubation of the cells with anti-L chain antibody, whereas preincubation with normal rabbit IgG resulted in almost complete inhibition. To our knowledge this is the first demonstration of antigen binding to PBL from agammaglobulinemic chickens.