The primary immunodeficiencies (1)

How to: Diagnose inborn errors of intrinsic and innate immunity to viral, bacterial, mycobacterial, and fungal infections

BACKGROUND

Inborn errors of intrinsic and innate immunity constitute the focus of a growing research field that investigates the molecular mechanisms underlying susceptibility to infections previously not considered part of the spectrum of inborn errors of immunity. These so-called nonconventional inborn errors of immunity often occur as infections caused by a narrow spectrum of microorganisms in otherwise healthy subjects.

OBJECTIVES

This review aimed to provide a framework for identifying and evaluating patients with viral, bacterial, mycobacterial, and fungal infection needing further assessment for inborn errors of intrinsic and innate immunity.

SOURCES

A literature search was performed using PubMed, from inception until 1 May 2022. The search included the following keywords: "inborn errors of immunity"; "inborn errors of innate immunity"; "primary immune deficiency"; "primary immunodeficiency"; "infections"; "infectious susceptibility"; "virus"; "pyogenic bacteria"; "mycobacteria"; "fungi". All article types were considered.

CONTENT

We review the definition of what can be considered an inborn error of immunity and how the definition changed over the last ∼25 years. We further provide criteria to rule out secondary immunodeficiencies, identify patients needing further clinical and laboratory immunological assessment, and suspect and diagnose an inborn error of intrinsic and innate immunity. These steps are proposed as part of an algorithm.

IMPLICATIONS

Patients with unexplained life-threatening infections, including otherwise healthy subjects, should be systematically screened for known inborn errors of immunity. The early diagnosis can prevent recurrence of life-threatening infections in the patients and reduce the total burden of infectious diseases.

The clinical features and infectious etiologies of acute diarrhea in immunocompromised hosts

Objectives The acute diarrhea is a common complaint among immunocompromised hosts, and may cause life threatening event. The infectious etiologies vary depending on virus, bacteria, and parasites. The most common etiology of acute gastroenteritis is known as enteric virus in Korea. But there are few studies about the infectious etiology of acute gastroenteritis in immunocompromised hosts. The aim of this study was to investigate the infectious etiologies of acute diarrhea in immunocompromised hosts. Methods Seventy three patients were enrolled prospectively in a university hospital from January 2013 to July 2014. Immunocompromised hosts included above 65-year-old people, patients with chronic diseases, solid organ or stem cell transplants, solid organ malignancies, hematologic malignancies, immunosuppressive or steroid taking patients. The clinical data were collected and stool samples collected during diarrhea were undergone laboratory analysis for enteric viruses and bacterial enteropathogens including Salmonella spp., Shigella spp., and Clostridium difficile. Results Fifty five patients were analyzed as follows : above 65 year-old people were 36 cases (66%), previous antibiotic usage was 22 cases (41.5%). 44 cases (81.1%) were admitted to general ward whereas 9 cases to ICU (17%). 41 cases (73.6%) were treated with antibiotics. Positive C. difficile toxin assays were 6 cases (11.9%). Other infectious etiologies were not found. Conclusions C. difficile infection was more common infectious etiology while enteric viruses and other bacteria are not associated with acute diarrhea among immunocompromised hosts in this study. So C. difficile infection must be considered preferentially in immunocompromised hosts with acute diarrhea.

Immunopathogenesis of granulomas in chronic autoinflammatory diseases

Granulomas are clusters of immune cells. These structures can be formed in reaction to infection and display signs of necrosis, such as in tuberculosis. Alternatively, in several immune disorders, such as sarcoidosis, Crohn's disease and common variable immunodeficiency, non-caseating granulomas are formed without an obvious infectious trigger. Despite advances in our understanding of the human immune system, the pathogenesis underlying these non-caseating granulomas in chronic inflammatory diseases is still poorly understood. Here, we review the current knowledge about the immunopathogenesis of granulomas, and we discuss how the involved immune cells can be targeted with novel therapeutics.

Analysis of clinical presentations of Bruton disease: a review of 20 years of accumulated data from pediatric patients at Severance Hospital

PURPOSE

X-linked agammaglobulinemia (XLA) is a humoral immunodeficiency disease caused by a mutation in the Bruton tyrosine kinase (BTK) gene resulting in defective B cell differentiation. Because it is a relatively rare disorder, it is difficult for clinicians to have a comprehensive understanding of XLA due to a lack of exposure to the disease. Clinical presentations of patients with XLA were analyzed and discussed to improve care plans.

MATERIALS AND METHODS

During a 20 year period, from January 1987 to June 2006, a total of 19 patients were diagnosed as XLA in the Department of Pediatrics at Severance Hospital, Seoul, Korea. A retrospective analysis of the clinical presentations of those patients was performed.

RESULTS

The mean age of the XLA patients included in the study was 4.89 years, with a range of 6 months to 13 years. Twelve patients were diagnosed before age 5, while the other 7 patients were diagnosed after age 5. Recurrent infections observed in the patients included pneumonia, acute otitis media, septic arthritis, skin infection, sepsis, sinusitis, acute gastroenteritis, cervical lymphadenitis, epididymitis, meningitis, osteomyelitis, urinary tract infection and encephalitis. Frequency of admissions was variable from 0 to 12 times, depending on the time at which immunoglobulin therapy was started. Six cases had family histories positive for XLA. BTK gene mutations were found in 8 cases.

CONCLUSION

The overall prognosis of XLA is good as long as patients are diagnosed and treated early with regular intra venous gamma globulin therapy before the sequelae of recurrent infections appear.

The evolution of adaptive immunity

Approximately 500 mya two types of recombinatorial adaptive immune systems appeared in vertebrates. Jawed vertebrates generate a diverse repertoire of B and T cell antigen receptors through the rearrangement of immunoglobulin V, D, and J gene fragments, whereas jawless fish assemble their variable lymphocyte receptors through recombinatorial usage of leucine-rich repeat (LRR) modular units. Invariant germ line-encoded, LRR-containing proteins are pivotal mediators of microbial recognition throughout the plant and animal kingdoms. Whereas the genomes of plants and deuterostome and chordate invertebrates harbor large arsenals of recognition receptors primarily encoding LRR-containing proteins, relatively few innate pattern recognition receptors suffice for survival of pathogen-infected nematodes, insects, and vertebrates. The appearance of a lymphocyte-based recombinatorial system of anticipatory immunity in the vertebrates may have been driven by a need to facilitate developmental and morphological plasticity in addition to the advantage conferred by the ability to recognize a larger portion of the antigenic world.

Btk expression is controlled by Oct and BOB.1/OBF.1

BOB.1/OBF.1 is a lymphocyte-restricted transcriptional coactivator. It binds together with the Oct1 and Oct2 transcription factors to DNA and enhances their transactivation potential. Mice deficient for the transcriptional coactivator BOB.1/OBF.1 show several defects in differentiation, function and signaling of B cells. In search of BOB.1/OBF.1 regulated genes we identified Btk—a cytoplasmic tyrosine kinase—as a direct target of BOB.1/OBF.1. Analyses of the human as well as murine Btk promoters revealed a non-consensus octamer site close to the start site of transcription. Here we show that Oct proteins together with BOB.1/OBF.1 are able to form ternary complexes on these sites in vitro and in vivo. This in turn leads to the induction of Btk promoter activity in synergism with the transcription factor PU.1. Btk, like BOB.1/OBF.1, plays a critical role in B cell development and B cell receptor signalling. Therefore the down-regulation of Btk expression in BOB.1/OBF.1-deficient B cells could be related to the functional and developmental defects observed in BOB.1/OBF.1-deficient mice.

Semiquantitative evaluation of mRNAs for the membranous form of immunoglobulin heavy chain is useful for investigating the etiology in CVID

Common variable immunodeficiency (CVID) is a primary antibody deficiency syndrome characterized by defective B-cell maturation and antibody formation resulting in low serum antibody levels of all immunoglobulin (Ig) isotypes. To investigate the pathogenesis of CVID, we developed a set of competitive polymerase chain reaction for membrane-bound Ig heavy chain (mHC) mRNAs for IgM, IgG and IgA. Data on three children with CVID in group A of Bryant's classification were analysed. All the three mHC mRNA levels in Patient 1 were almost same as those in healthy controls. In Patient 2, mHC mRNA for IgM was detected at a level similar to that in controls, but mHC mRNAs for IgG and IgA heavy chains were not detected. In Patient 3, all the three mHC mRNAs were undetectable. Our data suggest that a different molecular basis exists in these patients with CVID even though all belong to group A of Bryant's classification. Use of our method facilitates a better understanding of molecular events in CVID patients and may be useful for precise classifications of CVID.

Immunosurveillance, immunodeficiency and lymphoproliferations

The incidence of malignant lymphomas is significantly higher in patients who have congenital or acquired immunodeficiencies. Although there are some differences between these immunodeficiency-associated lymphoproliferative disorders (IALD), they share several features: a tendency to present in extranodal sites, particularly the central nervous system and gastrointestinal tract, rapid clinical progression when untreated, diffuse large cell histology, B-cell origin and association with the Epstein-Barr virus (EBV). In the presence of disturbed T-cell function EBV may induce not only prolonged proliferation but also transformation of B-cells. In patients with primary, congenital immunodeficiency the incidence of IALD ranges from 0.7% for patients with X-linked agammaglobulinemia to 12-15% in patients with ataxia telangiectasia. In patients with post-transplant lymphoproliferative disorders (PT-LPD) the incidence varies from 0.5% after bone marrow transplantation to 10% after heart-lung transplantation. PT-LPD are often characterized by a polymorphic cell population. Recent studies identified three categories: plasmacytic hyperplasia, polymorphic lymphoproliferation and B-cell non-Hodgkin's lymphoma (NHL). The plasmacytic hyperplasias are of polyclonal composition, while polymorphic lymphoproliferations and NHL are monoclonal. The precise risk of lymphoma development in HIV infection is not defined, but estimates suggest a prevalence of 3-4%. HIV-related NHLs are divisible by site of manifestation into systemic, primary central nervous system and body-cavity lymphomas, and by pathology into Burkitt's and Burkitt's-like lymphoma, and diffuse large cell lymphoma (DLCL). In about 90% of cases these lymphomas are of monoclonal B-cell composition. Recent experiences suggest a link between therapy with immunosuppressive drugs (methotrexate, azathioprine, cyclophospamide, etc.) and development of IALD, best supported by the increased rate of IALD in patients with rheumatoid arthritis who receive methotrexate therapy. The occurrence of IALD demonstrates the importance of competent immunosurveillance in the development of lymphoid neoplasias, which may have therapeutic relevance too.

Thymic malignancies

Thymomas and thymic carcinomas are unique tumors of the anterior mediastinum. The association of a variety of different paraneoplastic syndromes with such lesions has fascinated physicians and researchers for years. Most recently, it has been demonstrated by numerous authors that thymomas are chemosensitive tumors. Their indolent nature and relative rarity have made evaluation through prospective randomized clinical trials extremely difficult. Further information regarding the molecular nature of these neoplasms and immunologic aspects is needed in future investigation.

Bacteremia and skin/bone infections in two patients with X-linked agammaglobulinemia caused by an unusual organism related to Flexispira/Helicobacter species

Two patients with Bruton's X-linked agammaglobulinemia are described with bacteremia and skin/bone infection due to an organism which by 16S rRNA gene sequence analysis was most closely related to "Flexispira" rappini (and thus designated a Flexispira-like organism, FLO) and more distantly related to the Helicobacter species. The organism required microaerobic conditions and, supplemental H(2) gas for growth and was reliably stained with acridine orange. In common with Helicobacter cinaedi infections, the focus of the FLO infection was in one case in the blood vessels or lymphatics of an extremity and in the other case in the skin and adjacent bone of an extremity. In both cases, prolonged IV antibiotic therapy was necessary to clear the infection. The susceptibility of XLA patients to FLO infection appears to be related to the fact that XLA is associated with severe B cell (humoral) immunodeficiency and thus these patients have difficulty with intravascular or intralymphatic infection. These findings elucidate the nature of FLO infections in humans and point the way to their detection and treatment.

Bilateral consecutive central corneal perforations associated with hypogammaglobulinemia

OBJECTIVE

To describe the presentation and the clinical course of a patient with consecutive central sterile corneal perforations associated with common variable immunodeficiency.

DESIGN

Case report.

METHODS

Multiple corneal cultures and scrapings were performed in an effort to identify an infectious cause and all were negative. Corneal biopsy did not demonstrate any evidence of micro-organisms. An extended investigation failed to uncover a collagen vascular cause or atopy.

RESULTS

Progressive sterile stromal thinning with intact epithelium in the left eye proceeded to perforation despite topical treatment, and cyanoacrylate gluing was performed. However, a secondary Haemophilus influenza endophthalmitis developed, and the eye was eventually lost. The fellow eye proceeded along the same clinical course with sterile stromal thinning. A lamellar patch graft was performed when the central ulceration progressed to a descemetocele. The eye remained quiet with 20/25 vision for 2 years, until the patient died from complications of a liver transplant.

CONCLUSIONS

Devastating central sterile corneal thinning leading to perforation may occur in patients with hypogammaglobulinemia.

Up-regulation of IL-12 in monocytes: a fundamental defect in common variable immunodeficiency

We show that LPS-stimulated circulating CD14-positive monocytes from patients with common variable immunodeficiency (CVID) express a higher proportion of intracellular IL-12-positive cells than monocytes from patients with X-linked agammaglobulinemia or normal subjects. We used four-color flow cytometry and measured IL-12 with an Ab to the p40 subunit following stimulation with LPS. The raised IL-12 is associated with an increased frequency of IFN-gamma-positive T cells, but not of IFN-gamma-positive CD56+ NK cells. These increases in frequency of cytokine-positive cells are due to a decrease in the absolute numbers of circulating monocytes and T cells that are negative for IL-12 and IFN-gamma, respectively. The increased frequency of IL-12-positive monocytes appears to be selective because TNF-alpha was not increased, and is thus unlikely to reflect a general activation. Chronic infection is also unlikely to explain our data since cells from X-linked agammaglobulinemia patients with a similar Ig deficiency do not show these changes. Our data suggest a fundamental abnormality in the IL-12/IFN-gamma circuit in CVID, with up-regulation of IL-12 being the "primary" factor. This imbalance is likely to skew the immune response away from Ab production and also explains the failure of CVID T cells to make Ag-specific memory cells and the chronic inflammatory and granulomatous complications that are a feature of CVID. This disease appears to be a rare example of a polarized Th1-type response and may in part be due to a genetic defect in the control of IL-12 production.

Cutting edge: lack of peripheral B cells and severe agammaglobulinemia in mice simultaneously lacking Bruton's tyrosine kinase and the B cell-specific transcriptional coactivator OBF-1

OBF-1 is a B cell-restricted transcriptional coactivator that is recruited to octamer-containing promoters by interacting with the POU domain of Oct-1 or Oct-2. We have shown earlier that mice lacking OBF-1 were dramatically impaired in their ability to mount humoral immune responses and did not develop germinal centers in the spleen; however, they had a largely normal B cell development in the bone marrow. In this study, we demonstrate that OBF-1-deficient mice also have an early defect in B cell development and show that OBF-1-/- immature B cells are greatly impaired at the transition from the bone marrow to the spleen. In addition, when the OBF-1 mutation is combined to a mutation in the gene encoding Bruton's tyrosine kinase, a striking phenotype is observed. These double-deficient animals lack peripheral B cells and have virtually no serum Igs, thus closely resembling human X chromosome-linked agammaglobulinemia.

Stress, depression and immunity: the role of defense and coping styles

It is by now widely recognized that acute and chronic stress have an impact on the immune system. Acute stress may have a stimulating effect on the immune system, while in the case of chronic stress--and in particular in depression--the immune system may be down-regulated. However, there is considerable individual variability in the immune response to stress. This seems to a large extent to be determined by the subject's way of dealing with stress. The perception and evaluation of a stressor and the specific ways of stress coping may in different ways be related to various aspects of the stress response: sympathetic nervous system (SNS) activation and activation of the hypothalamic-pituitary-adrenal (HPA) axis, both systems affecting the immune system. Prolonged exposure to stressors or to severe life stresses may outweigh the person's coping resources leading to feelings of depression. The affective changes with the accompanying changes in the HPA axis are one of the hypothesized mechanisms underlying the immune changes in depression. It should be noted that the relationship between depression and immunity is affected by several other factors, such as gender and age and other personal resources. Increasing the subject's abilities to cope with stress and to reduce the negative affect by psychological interventions may on the other hand have a beneficial effect on the immune system.

B-1 cell development: evidence for an uncommitted immunoglobulin (Ig)M+ B cell precursor in B-1 cell differentiation

Murine phosphatidyl choline (PtC)-specific B cells in normal mice belong exclusively to the B-1 subset. Analysis of anti-PtC (VH12 and VH12/Vkappa4) transgenic (Tg) mice indicates that exclusion from B-0 (also known as B-2) occurs after immunoglobulin gene rearrangement. This predicts that PtC-specific B-0 cells are generated, but subsequently eliminated by either apoptosis or differentiation to B-1. To investigate the mechanism of exclusion, PtC-specific B cell differentiation was examined in mice expressing the X-linked immunodeficiency (xid) mutation. xid mice lack functional Bruton's tyrosine kinase (Btk), a component of the B cell receptor signal transduction pathway, and are deficient in B-1 cell development. We find in C57BL/ 6.xid mice that VH12 pre-BII cell selection is normal and that PtC-specific B cells undergo modest clonal expansion. However, the majority of splenic PtC-specific B cells in anti-PtC Tg/xid mice are B-0, rather than B-1 as in their non-xid counterparts. These data indicate that PtC-specific B-0 cell generation precedes segregation as predicted, and that Btk function is required for efficient segregation to B-1. Since xid mice exhibit defective B cell differentiation, not programmed cell death, these data are most consistent with an inability of PtC-specific B-0 cells to convert to B-1 and a single B cell lineage.

Screening patients affected by common variable immunodeficiency

Chronic immunoglobulin administration decreases the incidence of bronchial and pulmonary infections in patients affected by chronic variable immunodeficiency (CVI). In this study, an ENT screening was carried out in 22 patients affected by chronic variable immunodeficiency and treated with chronic immunoglobulin administration. All the patients underwent ENT physical examination, nasal endoscopy by fiberoptics, mucociliary transport test (MTT), anterior rhinorheomanometry (RRM), nasal provocation test with cold water (ANPT), audiometry and impedentiometry, olfactory evaluation, and paranasal sinus X rays. Dysphagia was present in 91% of the patients, nasal secretion and obstruction in 77%, and hypoacusia, tinnitus, and otodinia in 57%. Rhinitis and pharyngitis were observed in 86% of the patients, and serous middle ear effusion in 50%. Confirmed maxillary sinusitis was observed in five patients. Hyposmia was observed in 50% of the patients. MTT was significantly longer in the patients than in the controls (18.0 +/- 10.5 vs. 11.2 +/- 2.4 min; p < .05). Nasal resistance was lower in patients than in controls (0.46 +/- 0.32 vs. 1.11 +/- 0.22 Pa/L.s-1; p < .001). ANPT was positive in 9 patients out of 25 versus 1 control out of 15 (p < .05). Finally, seven patients were affected by transmissive hypoacusia, and one patient by neurosensorial hypoacusia. Our results suggest that chronic immunoglobulin administration in CVI patients is not effective against ENT disorders, probably because of the important role played by nasal hyperreactivity. Frequent ENT examination and early treatment of ENT disorders are therefore suggested in order to prevent chronic disease.

Large-scale comparative sequence analysis of the human and murine Bruton's tyrosine kinase loci reveals conserved regulatory domains

Large-scale genomic DNA sequencing of orthologous and paralogous loci in different species should contribute to a basic understanding of the evolution of both the protein-coding regions and noncoding regulatory elements. We compared 93 kb of human sequence to 89 kb of mouse sequence in the Bruton's tyrosine kinase (BTK) region. In addition to showing the conservation of both position and orientation of the five functionally unrelated genes in the region (BTK, alpha-D-galactosidase A, L44L, FTP-3, and FCI-12), the comparison revealed conservation of clusters of noncoding sequence flanking the first exon of each gene. Furthermore, in the sequence comparison at the BTK locus, the conservation of clusters of noncoding sequence extends throughout the locus; the noncoding sequence is more highly conserved in the BTK locus in comparison to the flanking loci. This suggests a correlation with the complex developmental regulation of expression of btk. To determine whether a highly conserved 3.5-kb segment flanking the first exon of BTK contains transcriptional regulatory signals, we tested various portions of the segment for promoter and expression activity in several appropriate cell lines. The results demonstrate the contribution of the conserved region flanking the first exon to the cell lineage-specific expression pattern of btk. These data show the usefulness of large scale sequence comparisons to focus investigation on regions of noncoding sequence that play essential roles in complex gene regulation.

Immune and physiological responses of turkeys with green-liver osteomyelitis complex

A study of field turkeys was undertaken in order to determine the involvement of relative immunological differences in the etiology of turkey osteomyelitis complex (TOC). Lame and normal turkeys were sampled from commercial flocks just prior to processing in two separate trials. After testing for functions of both humoral and cellular immunity, the turkeys were necropsied and examined for lesions of TOC. There were significantly higher relative spleen and over weights and significantly lower body weights and relative bursal weights in birds with TOC. The birds with TOC had lower response to phytohemagglutinin-P in both in vivo and in vitro tests as well as lower circulating lymphocyte counts and higher monocyte, heterophil, and total white blood cell counts. There was a significantly higher antibody response to sheep red blood cells in turkeys with TOC, whereas antibody response to Salmonella pullorum antigen was not different. There were no significant differences in the percentages of mononuclear cells or heterophils able to phagocytize bacteria or latex particles, or kill bacteria; however, the heterophils from turkeys with TOC lesions did phagocytize significantly fewer latex particles per cell than did those of the healthy turkeys. Total serum protein, uric acid, and blood urea nitrogen levels were higher in birds with TOC, whereas hemoglobin, iron, alkaline phosphatase, and gamma-glutamyl-transferase levels were lower. Although many of the differences in birds with TOC could be caused by the normal host reaction to infection, further study may reveal innate differences that contribute to susceptibility to TOC.

X-linked agammaglobulinemia (XLA): a genetic tyrosine kinase (Btk) disease

X-linked agammaglobulinemia is a heritable immunodeficiency disease caused by a differentiation abnormality, resulting in the virtual absence of B lymphocytes and plasma cells. The affected gene encodes a cytoplasmic protein tyrosine kinase, Bruton's agammaglobulinemia tyrosine kinase, designated Btk. Btk and the other family members, Tec, ltk and Bmx, contain five regions, four of which are common structural and functional modules that are found in other signaling proteins. Mutations affect all domains of the gene, but amino acid substitutions seem to be confined to certain regions. More than 150 unique mutations have been identified and are collected in a mutation database, BTKbase. Here we discuss the three-dimensional structural implications of such mutations and their putative functional role. Of special interest are mutations affecting the pleckstrin homology domain, as Btk is the only disease-associated protein so far reported to carry mutations in this particular module.

Sarcoidosis and common variable immunodeficiency. Report of 8 cases and review of the literature

The true incidence of sarcoidosis in common variable immunodeficiency (CVID) is unknown. We report here 8 cases of sarcoidosis among 80 patients with CVID followed in our clinics, along with 22 well-documented cases reported in the literature. Sarcoidosis, therefore, represents an important entity to consider among patients with CVID who exhibit clinical, radiographic, laboratory, and biopsy findings compatible with sarcoidosis. Conversely, the diagnosis of CVID should be considered in patients with sarcoidosis who do not exhibit the characteristic hypergammaglobulinemia and who have a history of recurrent infections. Although many features of sarcoidosis are similar in patients with CVID to those in patients with sarcoidosis alone, there are many important differences. Patients with CVID in whom sarcoidosis develops present with hypogammaglobulinemia rather than hypergammaglobulinemia and have a higher prevalence of recurrent infections, thrombocytopenia, and splenic involvement. Steroids, in most cases, appeared helpful in reducing adenopathy and splenomegaly, improving uveitis, lowering serum alkaline phosphatase, and reversing hematologic abnormalities. The underlying pathophysiology responsible for the association of these 2 disorders in the same patient remains obscure. However, as more patients are identified, it may be possible to gain a better understanding of the immunologic defect responsible for the dual presentation of these 2 relatively uncommon diseases.

Consequences of hypogammaglobulinemia and steroid therapy in severe bronchopulmonary dysplasia

We retrospectively studied the relation between corticasteroid therapy, hypogammaglobulinemia (HG), and recurrent infections in 37 infants with moderate to severe bronchopulmonary dysplasia (BPD). Nineteen of the 37 patients had tracheostomies because of chronic respiratory failure. We hypothesized that recurrent infections were most prevalent in infants whose IgG levels remained low at one year of age (persistent HG) and in infants receiving high doses of corticosteroids during the first year of life. We further hypothesized that the duration of HG was strongly correlated with the cumulative first year steroid dose. We also studied the response to intravenous gammaglobulin (IVIG) replacement therapy in this population of BPD infants. Our results showed an association between first year corticosteroid dose, duration of HG (r = 0.49, p < 0.003), and frequency of infections (r = 0.51, p < 0.001). We noted a relatively strong correlation between frequency of infections and duration of HG (r = 0.84, p < 0.0001). Twenty-four of 37 (65%) infants showed persistent HG and 49% had evidence of abnormal specific antibody production. Sixty-four percent of infants studied had reduced lymphocyte responsiveness to mitogen stimulation. Nineteen of 37 (51%) infants required IVIG for an average duration of 17.9 months due to recurrent infections. The average number of infections per year decreased from 10.6 to 2.8 (t = 12.32, p < 0.0001). There were no complications associated with IVIG therapy, but one infant died of bronchiolitis obliterans following heart-lung transplantation. Eight of 37 (22%) infants have persistent immunologic dysfunction requiring ongoing IVIG at four years or more of follow-up. We conclude that a substantial number of ill infants with BPD will have immune dysfunction characterized by persistently low IgG levels and reduced specific antibody responsiveness to protein antigens. We speculate that these findings are related to the cumulative dose of corticosteroids received in the first year of life and to the severity of underlying disease.

Adult immunodeficiency and rheumatic disease

Several rheumatic illnesses may develop in adults with primary or acquired immunologic defects. Individuals with primary defects in B-cell antibody production, such as common variable immunodeficiency of selective IgA deficiency, and those with defects of complement components, have an increased prevalence of systemic lupus erythematosus--like syndromes or other autoimmune diseases. Defects in immunoglobulin production may be complicated by inflammatory or infectious arthritis. Infection with HIV-1 may be associated with diverse rheumatic conditions, including diffuse infiltrative lymphocytosis syndrome, myopathies, vasculitides, inflammatory arthritides, and infectious musculoskeletal complications. An approach to these disorders that takes into consideration the underlying mechanism of disease is presented. Appropriate strategies aimed at treatment of the underlying immunodeficiency may improve the clinical course of the associated rheumatic disorder.

Mutation analysis of the gene encoding Bruton's tyrosine kinase in a family with a sporadic case of X-linked agammaglobulinemia reveals three female carriers

Bruton's tyrosine kinase (Btk) has been identified as the protein responsible for the primary immunodeficiency X-linked agammaglobulinemia (XLA). We and others have cloned the gene for Btk and recently reported the genomic organization. Nineteen exons were positioned within the 37 kb gene. With the sequence data derived from our genomic map, we have designed a PCR based assay to directly identify mutations of the Btk gene in germline DNA of patients with XLA. In this report, the assay was used to analyze a family with a sporadic case of XLA to determine if other female relatives carry the disease. A four base-pair deletion was found in the DNA of the affected boy and was further traced through three generations. With the direct identification of the mutations responsible for XLA, we can now diagnose conclusively the disease and identify the immunologically normal female carriers. This same technique can easily be applied to prenatal diagnosis in families where the mutation can be identified.

Defective lymphoid development in mice lacking Jak3

The Janus tyrosine kinases (Jaks) play a central role in signaling through cytokine receptors. Although Jak1, Jak2, and Tyk2 are widely expressed, Jak3 is predominantly expressed in hematopoietic cells and is known to associate only with the common gamma (gamma c) chain of the interleukin (IL)-2, IL-4, IL-7, IL-9, and IL-15 receptors. Homozygous mutant mice in which the Jak3 gene had been disrupted were generated by gene targeting. Jak3-deficient mice had profound reductions in thymocytes and severe B cell and T cell lymphopenia similar to severe combined immunodeficiency disease (SCID), and the residual T cells and B cells were functionally deficient. Thus, Jak3 plays a critical role in gamma c signaling and lymphoid development.

Otitis media following tympanostomy tube placement in children with IgG2 deficiency

Children with IgG2 deficiency commonly develop recurrent acute otitis media. It is believed that these infections are secondary to impaired antibody response rather than eustachian tube dysfunction and are therefore less responsive to treatment with tympanostomy tubes. The authors compared the incidence of acute otitis media in IgG2-deficient patients following tympanostomy tube placement with controls in a retrospective cohort study. The charts of 20 patients (10 with IgG2 deficiency and 10 controls) were reviewed. Episodes of otitis media were recorded for 12 months. IgG2-deficient patients experienced three times as many occurrences of otitis media as did controls. This suggests that otitis media is much more common in these patients following tympanostomy tube placement. We believe that an immunodeficiency workup should be considered in patients with multiple episodes of otitis media following placement of tympanostomy tubes.

Defective B cell development and function in Btk-deficient mice

Mutations in the Bruton's tyrosine kinase (Btk) gene have been linked to severe early B cell developmental blocks in human X-linked agammaglobulinemia (XLA), and to milder B cell activation deficiencies in murine X-linked immune deficiency (Xid). To elucidate unequivocally potential Btk functions in mice, we generated mutations in embryonic stem cells, which eliminated the ability to encode Btk pleckstrin homology or kinase domains, and assayed their effects by RAG2-deficient blastocyst complementation or introduction into the germline. Both mutations block expression of Btk protein and lead to reduced numbers of mature conventional B cells, severe B1 cell deficiency, serum IgM and IgG3 deficiency, and defective responses in vitro to various B cell activators and in vivo to immunization with thymus-independent type II antigens. These results prove that lack of Btk function results in an Xid phenotype and further suggest a differential requirement for Btk during the early stages of murine versus human B lymphocyte development.

An SH3-binding site conserved in Bruton's tyrosine kinase and related tyrosine kinases mediates specific protein interactions in vitro and in vivo

Mutations in Bruton's tyrosine kinase (Btk) have been associated with immunodeficiencies in man and in the mouse. Btk and two related proteins, Itk and Tec, are members of a distinct family of tyrosine kinases. These kinases are believed to function in various receptor-mediated signaling pathways, but their specific functions are as yet undefined. Btk and its homologues share extensive sequence similarity, including a conserved region, the Tec-homology (TH) domain, that has been proposed to mediate specific intermolecular or intramolecular interactions. The TH region of Btk contains a functional SH3-binding site at residues 189-192. SH3 binding is selective: Btk is retained by the SH3 domain of Fyn but not by that of Blk, another Src-type kinase. TH-SH3 binding in vitro is abolished by specific, single amino acid substitutions within the Btk TH domain or the Fyn SH3 domain. We provide two lines of evidence that the SH3-binding site in the Btk TH domain mediates protein interactions in intact cells. First, treatment of cells with pervanadate induces an increase in the phosphotyrosine content of kinase-inactive Btk; this response is substantially reduced by a mutation that inactivates the SH3-binding site in the Btk TH domain. Second, in cell lysates Btk is found in association with an as yet unidentified 72-kDa phosphotyrosine-containing protein; this interaction requires a functional SH3-binding site in the TH domain. The TH domain may therefore interact in vivo with other proteins that regulate the phosphorylation state of Btk.

Addison disease 10 years after bone marrow transplantation for Wiskott-Aldrich syndrome

We report a 10-year-old boy with familial Wiskott-Aldrich syndrome (WAS) who underwent successful bone marrow transplantation (BMT) at the age of 9 months. With the exception of auto-immune haemolytic anaemia due to warm antibodies lasting 15 months there had not been any complication after BMT. Ten years later the patient presented with diarrhoea, hyperpigmentation of skin and oral mucosa, fatigue and polyuria. Diagnosis of Addison disease was confirmed by typical electrolyte imbalance and absent cortisol response to adrenocorticotrophic hormone. Adrenal antibodies were positive. On therapy with oral gluco- and mineralocorticoids, the symptoms disappeared and electrolytes normalized. To our knowledge auto-immuno endocrinopathy after BMT for WAS has not yet been reported.

CONCLUSION

This is the first report of auto-immune adrenal insufficiency after BMT for WAS. The aetiopathogenesis of this condition remains unknown since auto-immune diseases as toxic side-effects of the ablative treatment before BMT have not yet been reported, and a relapse of WAS and cotransplantation of auto-immune adrenal insufficiency have been ruled out.

Structural basis for X-linked agammaglobulinemia (XLA): mutations at interacting Btk residues R562, W563, and A582

It has been suggested that tryptophan 563 is sandwiched between residues R562 and A582 in Bruton's agammaglobulinemia tyrosine kinase (Btk). Mutations of the surrounding residues have been shown to cause X-linked agammaglobulinemia. Substitutions R562P and A582V were noticed to have impaired kinase activity. However, based on Western blot analysis, the mutant proteins were expressed at normal levels. Molecular modeling of the kinase domain has previously indicated that these residues presumably govern the position of the W563 side chain, which is thought to interact with the catalytic loop. W563 is inside the molecule and too far away from the catalytic center to interact directly with the substrate or cofactors. To prove these model-based conclusions, a conservative substitution with phenylalanine for W563 was made, and the resultant mutant lacked kinase activity. These results confirm our previous assumption that the side chain of W563, invariant in protein tyrosine kinases, is crucial for Btk kinase activity. Mutations in the surrounding residues seem to inactivate Btk by affecting the location of W563.

Clinical patterns of X linked agammaglobulinemia in Malaysian children

X linked agammaglobulinemia (XLA) is rarely reported from developing countries especially from South East Asia. It appears that X linked agammaglobulinemia is less common in certain ethnic groups. It is very uncommon in black people in USA and South Africa. In multiracial Malaysia we have documented five XLA in Malays and Indians but not in the Chinese that constitute about 31% of the population. First degree relatives afflicted with XLA or other primary immunodeficiencies occurred more often in our study. All showed lung involvement although the etiologic organisms involved were atypical, being Gram negative.