Bruton's tyrosine kinase is not essential for LPS-induced activation of human monocytes

BACKGROUND

X-linked agammaglobulinemia (XLA) is characterized by impaired B-cell differentiation caused by mutations in the Bruton's tyrosine kinase (Btk) gene. The natural disease model, the X-linked immunodeficiency mouse, shows a less severe phenotype, indicating a different requirement of Btk in human and mouse B cells. Btk is also expressed in the myeloid line and participates in LPS signaling. Deficient oxidative burst and myeloid differentiation have been reported in the X-linked immunodeficiency mouse, but the precise mechanism and relevance of Btk activity in human monocytes is poorly understood.

OBJECTIVE

The apparent absence in XLA of clinical manifestations of myeloid deficiency prompted us to explore the relevance of complete Btk absence in human myeloid cells.

METHODS

Seven patients with XLA with BTK mutations conditioning a null protein expression were included in the study. Monocyte LPS-induced mitogen-activated protein kinase activation, TNF-alpha and IL-6 production in monocytes, and oxidative burst in monocytes and granulocytes were analyzed by means of flow cytometry.

RESULTS

We show that in response to LPS, Btk-null monocytes from patients with XLA induce early mitogen-activated protein kinase activation and intracellular TNF-alpha and IL-6 production with the same intensity as cells from age- and sex-matched control subjects. In addition, the oxidative burst in response to LPS and other stimulants was completely normal in Btk-null monocytes and neutrophils.

CONCLUSION

Our results indicate that Btk is not essential for early LPS signaling in human monocytes and that different Btk dependency might exist between human and mouse myeloid cells.

CLINICAL IMPLICATIONS

These findings provide a better understanding of XLA, and they show the differences between human XLA and murine Xid models.

A novel Wiskott-Aldrich syndrome protein (WASP) complex mutation identified in a WAS patient results in an aberrant product at the C-terminus from two transcripts with unusual polyA signals

Wiskott-Aldrich syndrome (WAS) is an X-linked recessive disorder characterized by immunodeficiency, thrombocytopenia and eczema. A broad spectrum of mutations in the WASP gene has been identified as causing the disease. In the present paper, we report on a patient affected by WAS with a novel complex mutation, characterized by a small 9 bp deletion followed by an inversion of 151 bp and a gross deletion of 4.3 kb within the Xp11.23 region. The small deletion and the inverted fragment are found in intron 11. The large deletion initiates downstream of exon 11 of the WASP gene, including exon 12, and a genomic region upstream of the promoter of the contiguous SUV39H1 gene. Expression studies of the mRNA of the patient's sample showed the presence of two aberrant transcripts that code for a protein of 519 amino acids. We demonstrate that these two transcripts differ in the 3' UTR region, and result from the use of two alternative polyadenylation signals. The severe phenotype of the patient correlates with the presence of an aberrant protein.

Independent mutational events are rare in the ATM gene: haplotype prescreening enhances mutation detection rate

Mutations in the ATM gene are responsible for the autosomal recessive disorder ataxia-telangiectasia (A-T). Many different mutations have been identified using various techniques, with detection efficiencies ranging from 57 to 85%. In this study, we employed short tandem repeat (STR) haplotypes to enhance mutation identification in 55 unrelated A-T families of Iberian origin (20 Spanish, 17 Brazilian, and 18 Hispanic-American); we were able to identify 95% of the expected mutations. Allelic sizes were standardized based on a reference sample (CEPH 1347-2). Subsequent mutation screening was performed by PTT, SSCP, and DHPLC, and abnormal regions were sequenced. Many STR haplotypes were found within each population and six haplotypes were observed across several of these populations. Single nucleotide polymorphism (SNP) haplotypes further suggested that most of these common mutations are ancestrally related, and not hot spots. However, two mutations (8977C>T and 8264_8268delATAAG) may indeed be recurring mutational events. Common haplotypes were present in 13 of 20 Spanish A-T families (65%), in 11 of 17 Brazilian A-T families (65%), and, in contrast, in only eight of 18 Hispanic-American families (44%). Three mutations were identified that would be missed by conventional screening strategies. In all, 62 different mutations (28 not previously reported) were identified and their associated haplotypes defined, thereby establishing a new database for Iberian A-T families, and extending the spectrum of worldwide ATM mutations.

Epistatic effects occurring among susceptibility and protective MHC genes in IgA deficiency

Immunoglobulin A deficiency (IgAD), the most prevalent primary immunodeficiency in Caucasian populations, shows strong evidence of polygenic inheritance with several associated genes being located in the major histocompatibility complex (MHC). Our aims were to determine which previously described MHC associations were primary and not secondary to a decrease or an increase in other MHC haplotype frequencies, to study the genetic interactions between all disease-associated MHC haplotypes and, finally, to ascertain the relative importance of protection vs susceptibility. A relative predispositional effect (RPE) study showed that in addition to the primary positive association of IgAD with HLA-DRB1*0102, DR3/TNFa2b3, and DR7 carrying haplotypes, DRB1*1501 was a marker of a primary protective factor in the Spanish population. Our data also indicate that the combined presence in an individual of two MHC susceptibility haplotypes notably increases the predisposition to the disease and that DRB1*1501 positive haplotypes eliminate the susceptibility conferred by any other MHC haplotype.

MHC susceptibility genes to IgA deficiency are located in different regions on different HLA haplotypes

Familial predisposition to IgA deficiency (IgAD) suggests that genetic factors influence susceptibility. Most studies support a polygenic inheritance with a susceptibility locus (designated IGAD1) in the MHC, but its exact location is still controversial. This study aimed to map the predisposing IGAD1 locus (or loci) within the MHC by investigating the pattern of association of the disease with several markers in the region. DNA-based techniques were used to type individual alleles of four polymorphic HLA genes (HLA-DR, -DQA1, -DQB1, and HLA-B), six microsatellites (all located between HLA-DR and HLA-B), and three single nucleotide polymorphisms on the TNF gene. The frequencies of these alleles were compared among ethnically matched populations comprising 182 patients and 343 controls. Additionally, we investigated parents and siblings of 100 of these patients. All four parental haplotypes were established in each family (n = 400), and transmission disequilibrium tests were performed. Surprisingly, our results did not support the hypothesis of a unique susceptibility gene being shared by all MHC susceptibility haplotypes. On HLA-DR1 and -DR7-positive haplotypes IGAD1 mapped to the class II region, whereas on haplotypes carrying HLA-DR3 the susceptibility locus mapped to the telomeric end of the class III region, as reported previously. Our results show how, in complex diseases, individuals may be affected for different genetic reasons and a single linkage signal to a region of a chromosome may actually be the result of disease-predisposing alleles in different linked genes in different pedigrees.

Tumor necrosis factor genomic polymorphism in Spanish IGA deficiency patients

Selective IgA deficiency (IgAD) is the most common form of primary immunodeficiency. Its association with genes within the major histocompatibility complex (MHC) has been repeatedly reported. Recently the susceptibility gene has been located in the class III region, around the tumor necrosis factor (TNF) cluster. In this study we have examined IgAD association with TNF-alpha gene promoter polymorphisms and TNFa and b microsatellites. No significant association was found with the former polymorphisms and the observed associations with TNFa2 allele and haplotypes TNFa2b1 and TNFa2b3 were proven to be secondary to their occurrence on the B14-DR1 and B8-DR3 haplotypes, previously reported to be associated with susceptibility to IgAD. However, a primary negative (protective) association was found between the TNFa10 allele and IgAD.

HLA class II homozygosity confers susceptibility to common variable immunodeficiency (CVID)

Most cases of CVID occur sporadically, but familial cases do also occur and 15% of the patients with the disease have first degree relatives with IgA deficiency (IgAD). Our purpose was to study CVID association with HLA class II alleles and to ascertain whether this disease shares a common genetic background with IgAD in our population. Patients with CVID (n = 42), were typed using gene amplification and sequence-specific oligonucleotide probing for HLA-DRB1, DRB3, DQA1 and DQB1 loci and their typing compared with that of 96 IgAD and 334 healthy controls. We observed a positive association between non-Asp residues at position 57 of the HLA-DQbeta chain and CVID, although much weaker than in IgAD. Further, we found an association between CVID and homozygosity for genes encoding HLA class II molecules, especially HLA-DQ, not seen in IgAD. The data support the hypothesis that a restricted diversity of HLA class II molecules may contribute to susceptibility to CVID.

Soluble interleukin 6 (IL-6) receptor and IL-6 levels in serum and synovial fluid of patients with different arthropathies

OBJECTIVE

We studied interleukin 6 (IL-6) and soluble IL-6 receptor (sIL-6R) in serum and synovial fluid (SF) to investigate their role in different arthropathies.

METHODS

IL-6 was measured by ELISA and bioassay and sIL-6R by ELISA, in 210 sera and 73 SF samples from 49 patients with rheumatoid arthritis (RA), 20 crystal deposition disease, 17 osteoarthritis (OA), 24 with other inflammatory arthropathies, and 100 controls. In all patients, disease activity was assessed by erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP); in patients with RA and other arthropathies pain, tender and swollen joints, and Ritchie index were also evaluated. Total leukocyte count in SF was determined.

RESULTS

There was good correlation between IL-6 ELISA and bioassay levels both in serum (r = 0.62, p = 0.0001) and in SF (r = 0.72, p = 0.0001). Serum IL-6 was detected only in patients with inflammatory arthritis and SF IL-6 was detected in all patient groups. Serum IL-6 correlated with swollen joints (r = 0.35, p = 0.05), ESR (r = 0.46, p = 0.001), and CRP (r = 0.46, p = 0.001) in RA; and with CRP (r = 0.89, p = 0.0001) in crystal deposition disease. SF IL-6 correlated with ESR (r = 0.54, p = 0.007) and CRP (r = 0.42, p = 0.04) in RA; with SF total leukocyte count (r = 0.61, p = 0.004) in crystal deposition disease; and with SF total leukocyte count (r = 0.61, p = 0.009) in OA. No correlations were found in the group with other inflammatory diseases. No correlations were found between sIL-6R and IL-6 or between sIL-6R and disease activity variables in any group of patients.

CONCLUSION

Unlike IL-6, sIL-6R is not produced at the site of inflammation and is not related to clinical or biological disease activity variables. Only in RA are both IL-6 and sIL-6R levels increased, suggesting that sIL-6R may reinforce the systemic effects of IL-6.

Identification of deletions in the btk gene allows unambiguous assessment of carrier status in families with X-linked agammaglobulinaemia

Mutations within the btk gene have recently been shown to cause X-linked agammaglobulinaemia (XLA). Altered patterns of DNA restriction fragments are seen by Southern blot analysis of DNA from affected patients with deletions in the btk gene. We have identified seven affected families in which altered restriction fragments can be used to diagnose and confirm the carrier status of female relatives of affected boys and in prenatal diagnosis.

Characterization of minor and major antigenic regions within the hepatitis B virus nucleocapsid

Hepatitis B core antibodies (anti-HBc) appear very early during the course of the hepatitis B virus infection and often persist years after viral clearance. In order to characterize the immunodominant domain of the HBcAg, the human immune response against the HBV nucleocapsid (HBcAg) was analyzed by using 14 synthetic peptides. Anti-HBc antibodies were detected by an indirect enzyme-linked immunosorbent assay (ELISA) with HBc peptides. Results suggest that the anti-HBc response is heterogeneous and directed against the whole primary structure of the HBc protein. Results also indicate that the epitopes recognized by anti-HBc antibodies can vary with the stages of the disease. In most sera from patients with serological evidence of acute HBV infection, anti-HBc antibodies recognized all the HBc peptides; conversely, after the acute phase, anti-HBc antibodies recognized predominantly epitopes located within the central region of the HBc protein from residue 74 to 123. Our results suggest that the HBV core protein is made up of two antigenic regions: a major one expressing a family of immunodominant epitopes from residue 74 to 123, whereas the minor encompasses the rest of the protein. The concept of the conformational nature of the unique HBcAg determinant is discussed, suggesting numerous families of linear epitopes.

Combined total deficiency of C7 and C4B with systemic lupus erythematosus (SLE)

The first inherited combined total deficiency of C7 and C4B complement components associated with SLE is described in a young female. Functional C7 assays showed a homozygous C7 deficiency in the propositus and her sister, and an heterozygous one in their parents. C4 molecular analyses showed that both the propositus and her mother had two HLA haplotypes carrying only C4A-specific DNA sequences and a normal C4 gene number. Thus, only C4A proteins could be expressed, with resultant normal C4 serum levels. The coexistence of a combined complete C7 and C4B deficiency may therefore abrogate essential functions of the complement cascade presumably related to immune complex handling and solubilization despite an excess of circulating C4A. These findings challenge the putative pathophysiological roles of C4A and C4B and stress the need to perform both functional assays and C4 allotyping in patients with autoimmune pathology and low haemolytic activity without low serum levels of a classical pathway complement component.

Large fragments of nef-protein and gp110 envelope glycoprotein from HIV-1. Synthesis, CD analysis and immunoreactivity

Chemical synthesis of large peptide fragments (from 18 to 66 amino acid residues long) of the gp110 envelope glycoprotein and of nef-protein from HIV-1 was achieved by the solid phase method. Stepwise assembling of the peptide chains was carried out automatically on 4-(oxymethyl)-phenylacetamidomethyl resin using the N-alpha-butyloxycarbonyl amino acids with benzyl-based side chain protecting groups. Two elongation protocols were used depending on the peptide chain length: a standard cycle, mainly characterized by a single coupling step (Boc-amino acid symmetrical anhydride in dimethylformamide), and an optimized one for large peptides, based on a double coupling strategy (Boc-amino acid symmetrical anhydride first in dimethylformamide, then in dichloromethane). Final cleavage of the peptide from the solid support was carried out by anhydrous hydrogen fluoride and crude peptides were purified by C18 reverse phase medium pressure liquid chromatography after molecular filtration. Characterization of the purified peptides was done by analytical HPLC, amino acid content determination, and circular dichroism analysis both in polar (H2O) and in non-polar (TFE) environments. Immunoreactivity of anti-nef positive sera from HIV-1 infected patients by ELISA with the synthetic peptides was investigated. The results showed four major antigenic regions of nef-protein and mainly the immunodominance of the N- and C-termini of the molecule. Several of these peptides should prove to be useful for both diagnosis and vaccination purposes.

Use of synthetic peptides for the detection of antibodies against the nef regulating protein in sera of HIV-infected patients

Human sera were tested for the presence of anti-nef antibodies by radioimmunoassay (RIA), with recombinant radiolabelled nef expressed in E. coli. Of the 300 HIV-positive sera tested by RIA, 70 +/- 5.3% were found to be anti-nef positive. Anti-nef antibodies bound to nef with a high affinity (K 0.5 = 2.2 x 10(-9) M). In 31 of the sera, the specificity of anti-nef antibodies was further analysed by enzyme-linked immunosorbent assay (ELISA) with large synthetic peptides ranging from 31 to 66 amino acid residues and spanning the total sequence of nef from HIV-1. The results obtained showed that the immunodominant antigenic sites of nef were located close to the N- and C-terminal regions of the molecule.

Identification of a common domain in calmodulin-activated eukaryotic and bacterial adenylate cyclases

Bordetella pertussis and Bacillus anthracis, two taxonomically distinct bacteria, secrete adenylate cyclase toxins that are activated by the eukaryotic protein calmodulin. The two enzymes contain a well-conserved stretch of 24 amino acid residues [Escuyer et al. (1988) Gene 71, 293-298]. Antibodies have been obtained against two synthetic heptadecapeptides, covering part of the conserved sequences. The anti-peptide antibodies specifically reacted in Western blots with the rat brain adenylate cyclase as well as with the two bacterial enzymes. Anti-rat brain adenylate cyclase serum contained antibodies that were retained by the immobilized peptides, and the affinity-purified antibodies yielded the same recognition pattern of the eukaryotic enzyme as did the unfractionated serum. These results indicate that the eukaryotic adenylate cyclase contains an epitope closely related to that specified by the conserved bacterial sequence. The synthetic peptides and the bacterial adenylate cyclases appeared to compete for ATP (KD of the ATP-peptide complex ca. 0.2 mM), suggesting that the conserved sequence may be part of the substrate binding site in these two enzymes.

Anti-IgA antibodies in selective IgA deficiency and in primary immunodeficient patients treated with gamma-globulin

Sera from 106 blood donors, 40 patients with primary immunodeficiencies (ID) treated with gamma-globulin, and 46 patients with selective IgA deficiency were analyzed by an enzyme-linked immunosorbent assay for anti-IgA antibodies. Increased levels of antibodies to IgA were found in 5.6% of the blood donors, 17.5% of the ID patients, and 36.8% of the isolated IgA deficiencies. The percentage was higher in patients with IgA and IgG2 deficiencies (50%). The percentage of patients having increased levels of anti-IgA antibodies was similar to the total prevalence of the 10 other autoantibodies studied. These anti-IgA antibodies were mainly of the IgG class, except from one blood donor with IgM antibodies, and two patients, one with isolated IgA deficiency and the other with common variable immunodeficiency who had anti-IgA antibodies of the IgE class. The latter patient developed a near fatal anaphylactic reaction when intravenous gamma-globulin was administered. Most of the patients with severe adverse reactions to gamma-globulin did not present anti-IgA antibodies. Our data suggest that at least in some immunodeficient patients the elevated amounts of anti-IgA antibodies are not related to the administration of exogenous IgA. The importance of measuring anti-IgA antibodies of the IgG and IgE isotypes in IgA-deficient patients as well as in patients in treatment with gamma-globulin is emphasized.

Hereditary myeloperoxidase deficiency: study of 12 cases

12 cases of hereditary myeloperoxidase (MPO) deficiency are reported. Histochemical stainings, lysosomal enzyme determinations, electron microscopic study of MPO and granulocytic function were performed. Family studies on 2 generations were carried out in 5 patients and histochemical stainings and biochemical lysosomal enzyme determinations were done. MPO deficiency was found to follow autosomal recessive inheritance and only rarely to have clinical effects.

Inhibition of neutrophil migration by serum IgA from patients with IgA nephropathy

Previously we showed that patients with IgA nephropathy present high serum levels of polymeric IgA and that in vitro polyclonal stimulation of their peripheral blood lymphocytes results in the synthesis of a large amount of true polymeric IgA. The aim of this study was to determine if the serum of patients with IgA nephropathy was capable of suppressing the directional migration of human normal polymorphonuclear cells (PMN), as do the polymeric fractions of IgA myeloma. Incubation of controls' PMN with fresh or heat-inactivated patients' plasma impaired the casein-induced directional migration significantly more than incubation with controls' plasma. This inhibitory effect was closely linked to polymeric IgA fractions and to a lesser extent with monomeric IgA immune complexes. The removal of IgA by immunoadsorption from patients' plasma completely abolished the migration suppression observed on controls' PMN. These results suggest that the high serum levels of polymeric IgA observed in patients with IgA nephropathy, by inhibiting directional migration and phagocytosis of PMN, and probably monocytes, could facilitate the persistent circulation and renal deposition of immune complexes.

Functional assessment of T and B lymphocytes in patients with selective IgM deficiency

Two patients with selective IgM deficiency were studied. Both presented with dermatitis, chronic diarrhoea, recurrent respiratory infections, failure to thrive, elevated serum IgE levels and in vivo impairment of antibody production. No phagocytic or complement abnormalities were found. B lymphocytes with surface IgM were present in normal or high percentage in peripheral blood, and produced normal amounts of IgM in vitro when co-cultured with normal T cells. Patients' T cells did not show excess suppressor function in vitro but had a decreased helper activity for IgM, IgG and IgA production. It is suggested that both patients have an extensive humoral immune deficiency that might be caused by the immunoregulatory T cell defect.

Ataxia-telangiectasia (A-T). Contribution with eighteen personal cases

Eighteen patients with ataxia-telangiectasia are presented. They belong to only one series. They are 7 males and 11 females aged between 17 months and 12 years. All of them presented the usual signs of the illness. There was more than one sibling affected in three families, in one of them three brothers and one second cousin of theirs. The immunological studies showed a deficit of IgA in 13 cases and an absence of IgG in one case. Six children died, one of which suffered from lymphosarcoma. The other appear to have died of infectious respiratory problems. The clinical picture deteriorated progressively in the majority of the cases, although in some of them a halt in the progression of the illness was observed for some time.

Neutrophil chemotaxis and serum chemotactic activity in systemic lupus erythematosus

Neutrophil chemotaxis, random motility, serum chemotactic activity derived from complement activation by classical or alternative pathways, and the presence of serum inhibitors of chemotaxis were all studied in 24 patients affected by Systemic Lupus Erythematosus (SLE) and in an equal number of healthy control subjects. Statistical comparison between patients and controls indicated lower chemotactic activity in patient's serum when activated by the classical pathway, and the presence in some SLE patients of a heat-labile inhibitor of the chemoattractants. Low "classical pathway" chemotactic indexes were correlated with low C4 values, active nephritis and recurrent infections. The presence of heat-labile inhibitor was correlated with low values of C3. Our data suggest that defective neutrophil chemotaxis could be one of the mechanisms contributing to the high incidence of infections suffered by SLE patients. The importance of conducting separate studies on cell movement and on generation of serum chemotactic activities by classical and alternative pathways in SLE patients is discussed.

A simple and reproducible method to evaluate granulocyte adherence

A simple method was devised to measure granulocyte adherence in whole blood. Columns of glass beads (4.5 mm diameter) in disposable plastic syringes were used. The assay showed great reproducibility when done in triplicate, the day to day variations in a given individual being minimal. Previous incubation of the blood with different ethanol concentrations diminished granulocyte adherence. The assay is easy to perform and does not require special equipment.

[Complement system in disseminated lupus erythematosus]

The levels of C3, C4 and CH50 in patients with lupus erythematosus disseminatus (LED) were lower than in the controls. However, although in many patients these levels were below the normal values, there was no statistically significant difference between the two group. The levels are reduced during the acute phases and in some patients they remain high. On the whole, C3 was lower in patients with nephropathy (p less than 0,025) than in patients presenting with clinical activity (p less than 0,02). The positive relationship existing between C3 and C4 (r = 0,641, p less than 0,01) suggests activation of the complement system in LED via the classic route. In cases with concurrent lupus nephropathy a relationship between C3 and C3PA was seen, suggesting that in this case the alternative route is involved.

Defective neutrophil motility in hypovitaminosis D rickets

The chemotactic activity and random motility of neutrophils, was studied in 38 patients with hypovitaminosis D rickets, and compared with 29 healthy controls of matched age. The chemotactic activity derived from the activated rickets serum as well as the amounts of the complement components C4, C3 and C5 was normal, but the cell motility was clearly defective (p less than 0.001). A possible relationship between defective neutrophil movement and the recurrent infections seen in these patients is suggested. The possible mechanisms responsible for the defect could be the alteration in Ca/P metabolism or a defective action of the vitamin D on the neutrophils.

Defective neutrophil chemotaxis and hyperimmunoglobulinemia E-a reversible defect?

An eleven-month-old boy is presented with chronic atopic dermatitis and recurrent infections of the skin and respiratory tract, including subcutaneous abscesses. Immunological studies disclosed a neutrophil chemotactic defect, blood eosinophilia and serum hyper IgE. The clinical and analytical data are similar to those of patients previously dermatitis reversed the chemotatic defect, the blood eosinophilia and the clinical symptoms.