Resolving the polygenic aetiology of a late onset combined immune deficiency caused by NFKB1 haploinsufficiency and modified by PIK3R1 and TNFRSF13B variants

Genetic variants in PIK3CD, PIK3R1 and NFKB1 cause the primary immune deficiencies, activated PI3Kδ syndrome (APDS) 1, APDS2 and NFκB1 haploinsufficiency, respectively. We have identified a family with known or potentially pathogenic variants NFKB1, TNFRSF13B and PIK3R1. The study's aim was to describe their associated immune and cellular phenotypes and compare with individuals with monogenic disease. NFκB1 pathway function was measured by immunoblotting and PI3Kδ pathway activity by phospho-flow cytometry. p105/p50 expression was absent in two individuals but elevated pS6 only in the index case. Transfection of primary T cells demonstrated increased basal pS6 signalling due to mutant PIK3R1, but not mutant NFKB1 or their wildtype forms. We report on the presence of pathogenic variant NFKB1, with likely modifying variants in TNFRSF13B and PIK3R1 in a family. We describe immune features of both NFκB1 haploinsufficiency and APDS2, and the inhibition of excessive PI3K signalling by rapamycin in vitro.

SARS-CoV-2 infection causes immunodeficiency in recovered patients by downregulating CD19 expression in B cells via enhancing B-cell metabolism

The SARS-CoV-2 infection causes severe immune disruption. However, it is unclear if disrupted immune regulation still exists and pertains in recovered COVID-19 patients. In our study, we have characterized the immune phenotype of B cells from 15 recovered COVID-19 patients, and found that healthy controls and recovered patients had similar B-cell populations before and after BCR stimulation, but the frequencies of PBC in patients were significantly increased when compared to healthy controls before stimulation. However, the percentage of unswitched memory B cells was decreased in recovered patients but not changed in healthy controls upon BCR stimulation. Interestingly, we found that CD19 expression was significantly reduced in almost all the B-cell subsets in recovered patients. Moreover, the BCR signaling and early B-cell response were disrupted upon BCR stimulation. Mechanistically, we found that the reduced CD19 expression was caused by the dysregulation of cell metabolism. In conclusion, we found that SARS-CoV-2 infection causes immunodeficiency in recovered patients by downregulating CD19 expression in B cells via enhancing B-cell metabolism, which may provide a new intervention target to cure COVID-19.

Identifying Safety Thresholds for Immunosuppressive Drugs: Applying Insights from Primary Antibody Deficiencies to Mitigate Adverse Events in Secondary Antibody Deficiencies Using Mathematical Modeling of Preclinical and Early Clinical Data

Immunosuppressive drugs can alleviate debilitating symptoms of autoimmune diseases, but, by the same token, excessive immune suppression can result in an increased risk of infection. Despite the dangers of a compromised immune system, clear definitions of what constitutes excessive suppression remain elusive. Here we review the most common infections associated with primary antibody deficiencies (PADs), such as agammaglobulinemia, common variable immunodeficiency (CVID), and IgA deficiency, as well as infections that are associated with drug-induced or secondary antibody immunodeficiencies (SADs). We identify a number of bacterial, viral, and fungal infections (e.g., Listeria monocytogenes, Staphylococcus sp., Salmonella spp., Escherichia coli, influenza, varicella zoster virus, and herpes simplex virus) associated with both PADs and SADs, and suggest that diagnostic criteria for PADs could be used as a first-line measure to identify potentially unsafe levels of immune suppression in SADs. Specifically, we suggest that, based on PAD diagnostic criteria, IgG levels should remain above 2-3 g/L, IgA levels should not fall below 0.07 g/L, and IgM levels should remain above 0.4 g/L to prevent immunosuppressive drugs from inducing mimicking PAD-like effects. We suggest that these criteria could be used in the early stages of drug development, and that pharmacokinetic and pharmacodynamic modeling could help guide patient selection to potentially improve drug safety. We illustrate the proposed approach using atacicept as an example and conclude with a discussion of the applicability of this approach for other drugs that may induce excessive immune suppression.

Congenital Athymia: Genetic Etiologies, Clinical Manifestations, Diagnosis, and Treatment

Congenital athymia is an ultra-rare disease characterized by the absence of a functioning thymus. It is associated with several genetic and syndromic disorders including FOXN1 deficiency, 22q11.2 deletion, CHARGE Syndrome (Coloboma, Heart defects, Atresia of the nasal choanae, Retardation of growth and development, Genitourinary anomalies, and Ear anomalies), and Complete DiGeorge Syndrome. Congenital athymia can result from defects in genes that impact thymic organ development such as FOXN1 and PAX1 or from genes that are involved in development of the entire midline region, such as TBX1 within the 22q11.2 region, CHD7, and FOXI3. Patients with congenital athymia have profound immunodeficiency, increased susceptibility to infections, and frequently, autologous graft-versus-host disease (GVHD). Athymic patients often present with absent T cells but normal numbers of B cells and Natural Killer cells (T-B+NK+), similar to a phenotype of severe combined immunodeficiency (SCID); these patients may require additional steps to confirm the diagnosis if no known genetic cause of athymia is identified. However, distinguishing athymia from SCID is crucial, as treatments differ for these conditions. Cultured thymus tissue is being investigated as a treatment for congenital athymia. Here, we review what is known about the epidemiology, underlying etiologies, clinical manifestations, and treatments for congenital athymia.

When the Good Syndrome Goes Bad: A Systematic Literature Review

Background

Good syndrome is a rare adult-onset immunodeficiency characterized by thymoma and hypogammaglobulinemia. Its clinical manifestations are highly heterogeneous, ranging from various infections to autoimmunity.

Objective

This study was to summarize patient characteristics, identify prognostic factors and define clinical subgroups of Good syndrome.

Methods

A systematic literature review was conducted to include patients with Good syndrome identified in PubMed, Embase and Cochrane databases between January 2010 and November 2020. Logistic and Cox regressions were used to identify prognostic factors impacting outcomes. Clinical subgroups were defined by multiple correspondence analysis and unsupervised hierarchical clustering. A decision tree was constructed to characterize the subgroup placement of cases.

Results

Of 162 patients included in the current study, the median age at diagnosis was 58 years and 51% were male. Type AB was the most common histological subtype of thymoma, and infections as well as concurrent autoimmune disorders were identified in 92.6% and 51.2% patients, respectively. Laboratory workup showed typical findings of combined immunodeficiency. Thymoma status (odds ratio [OR] 4.157, confidence interval [CI] 1.219-14.177, p = 0.023), infections related to cellular immunity defects (OR 3.324, 95% CI 1.100-10.046, p = 0.033), infections of sinopulmonary tract (OR 14.351, 95% CI 2.525-81.576, p = 0.003), central nerve system (OR 6.403, 95% CI 1.205-34.027, p = 0.029) as well as bloodstream (OR 6.917, 95% CI 1.519-31.505, p = 0.012) were independent prognostic factors. The 10-year overall survival was 53.7%. Cluster analysis revealed three clinical subgroups with distinct characteristics and prognosis (cluster 1, infections related to cellular immunity defects; cluster 2, infections related to other immunity defects; cluster 3, infections related to humoral and phagocytic immunity defects). A decision tree using infection types (related to humoral and cellular immunity defects) could place patients into corresponding clusters with an overall correct prediction of 72.2%.

Conclusions

Infection type and site were the main prognostic factors impacting survival of patients with Good syndrome. We identified three subgroups within Good syndrome associated with distinct clinical features, which may facilitate the study of underlying pathogenesis as well as development of targeted therapy.

Immunodeficiency and bone marrow failure with mosaic and germline TLR8 gain of function

Inborn errors of immunity (IEI) are a genetically heterogeneous group of disorders with a broad clinical spectrum. Identification of molecular and functional bases of these disorders is important for diagnosis, treatment, and an understanding of the human immune response. We identified 6 unrelated males with neutropenia, infections, lymphoproliferation, humoral immune defects, and in some cases bone marrow failure associated with 3 different variants in the X-linked gene TLR8, encoding the endosomal Toll-like receptor 8 (TLR8). Interestingly, 5 patients had somatic variants in TLR8 with <30% mosaicism, suggesting a dominant mechanism responsible for the clinical phenotype. Mosaicism was also detected in skin-derived fibroblasts in 3 patients, demonstrating that mutations were not limited to the hematopoietic compartment. All patients had refractory chronic neutropenia, and 3 patients underwent allogeneic hematopoietic cell transplantation. All variants conferred gain of function to TLR8 protein, and immune phenotyping demonstrated a proinflammatory phenotype with activated T cells and elevated serum cytokines associated with impaired B-cell maturation. Differentiation of myeloid cells from patient-derived induced pluripotent stem cells demonstrated increased responsiveness to TLR8. Together, these findings demonstrate that gain-of-function variants in TLR8 lead to a novel childhood-onset IEI with lymphoproliferation, neutropenia, infectious susceptibility, B- and T-cell defects, and in some cases, bone marrow failure. Somatic mosaicism is a prominent molecular mechanism of this new disease.

Immune function in childhood cancer survivors: a Children's Oncology Group review

Childhood cancer and its treatment often impact the haematopoietic and lymphatic systems, with immunological consequences. Immunological assessments are not routinely included in surveillance guidelines for most survivors of childhood cancer, although a robust body of literature describes immunological outcomes, testing recommendations, and revaccination guidelines after allogeneic haematopoietic cell transplantation. Survivorship care providers might not fully consider the impaired recovery of a child's immune system after cancer treatment if the child has not undergone haematopoietic cell transplantation. We did a scoping review to collate the existing literature describing immune function after childhood cancer therapy, including both standard-dose chemotherapy and high-dose chemotherapy with haematopoietic cell rescue. This Review aims to summarise: the principles of immunology and testing of immune function; the body of literature describing immunological outcomes after childhood cancer therapy, with an emphasis on the risk of infection, when is testing indicated, and preventive strategies; and knowledge gaps and opportunities for future research.

Beyond the adrenals: Organ manifestations in inherited primary adrenal insufficiency in children

Primary adrenal insufficiency (PAI) in children is mostly due to genetic defects. The understanding of the molecular genetics of the causes of adrenal insufficiency in the pediatric population has made significant progress during the last years. It has been shown that inherited PAI can lead to certain clinical manifestations and health problems in children beyond the adrenals. Organ dysfunctions associated with different forms of PAI in children include a wide range of organs such as gonads, brain, heart, bone, growth, bone marrow, kidney, skin, parathyroid, and thyroid. Diagnosing the correct genetic cause of PAI in children is therefore crucial to adequately control long-term treatment and follow-up in such patients.

Update on Advances in Hematopoietic Cell Transplantation for Primary Immunodeficiency Disorders

Hematopoietic stem cell transplantation (HSCT) in patients with primary immunodeficiency disorders (PIDDs) is being increasingly used as a curative option. Understanding the critical components, such as disease's nature and activity and pre-HSCT and post-HSCT patient care is key to a successful outcome. HSCT should be tailored to the underlying PIDD, as different PIDDs, such as severe combined immune deficiency, Treg dysfunction, and phagocytic disorders, have different transplant approaches. Therefore, successful HSCT in patients with PIDDs requires teamwork between immunologists and transplant physicians. In this article, the authors elaborate on various aspects of PIDD-HSCT and highlight recent advances.

The Treatment of Activated PI3Kδ Syndrome

Activated phosphoinositide 3-kinase δ syndrome (APDS), also known as PASLI disease (p110d-activating mutation causing senescent T cells, lymphadenopathy, and immunodeficiency) are combined immunodeficiencies resulting from gain-of-function mutations in the genes (PIK3CD and PIK3R1) encoding the subunits of phosphoinositide 3-kinase δ (PI3Kδ) and were first described in 2013. These mutations result in the hyperactivation of the PI3K/AKT/mTOR/S6K signally pathways. In this mini-review we have detailed the current treatment options for APDS. These treatments including conventional immunodeficiency therapies such as immunoglobulin replacement, antibiotic prophylaxis, and hematopoietic stem cell transplant. We also discuss the more targeted therapies of mTOR inhibition with sirolimus and selective PI3Kδ inhibitors.

Complications Associated with Underweight Primary Immunodeficiency Patients: Prevalence and Associations Within the USIDNET Registry

PURPOSE

The point prevalence of underweight status and obesity in primary immunodeficiency disease (PID) is unknown, despite the described associations between PID and weight loss and failure to thrive. The goal of this study is to estimate the prevalence of underweight status and obesity in PID patients and to investigate the associations between abnormal body weight and complications of PID.

METHODS

Using the US Immunodeficiency Network (USIDNET), we performed a retrospective analysis of 653 pediatric (age 2 to 20 years) and 514 adult (age > 20) patient records with information on patient body mass index (BMI). Prevalence of underweight and obese status in PID patients was compared to data from the National Health and Nutrition Examination Survey (NHANES).

RESULTS

After separating BMI data by year of entry to the database, we demonstrated that both adult and pediatric patients with PID had significantly higher prevalence of underweight patients in multiple years of analysis. Further examination of underweight patients by PID diagnosis revealed that underweight status in adults with CVID was associated with granulomatous disease as well as earlier age of CVID diagnosis. In the pediatric CVID cohort, underweight status was significantly associated with lymphopenia. Examination of obesity in pediatric and adult PID patients compared to NHANES database revealed only a single year when obesity in PID patients was significantly less prevalent. In other 2-year time intervals from 2005 to 2014, the prevalence of obesity was unchanged in children and adults.

CONCLUSIONS

These results quantify the prevalence of underweight status in PID in a North American population and demonstrate that whether as a result of weight loss or poor weight gain, underweight status is more prevalent in the PID population than in the general US population. The prevalence of obesity in PID patients was similar to that seen in the general population. This highlights the need for continued education on the association of low weight and PID.

CLINICAL TRIAL REGISTRATION

NCT01953016.

[Primary antibody deficiency syndromes]

Primary antibody deficiency syndromes (PAD) are a group of primary immunodeficiencies (PID) characterized by reduced production of immunoglobulins and recurrent respiratory tract infections. PAD varies from rare but life-threatening agammaglobulinaemias to frequent but often asymptomatic conditions such as selective immunoglobulin(Ig)A deficiency or IgG subclass deficiency. Common variable immunodeficiency is the clinically most important PAD. Hypogammaglobulinaemia may be associated with other PID or may be drug-induced or caused by infectious diseases, haematological malignancies or protein loss.

[Diagnosis and treatment of primary antibody deficiency syndromes]

Primary antibody deficiencies (PAD) make up more than half of primary immunodeficiencies. PAD is characterized by low levels of one or more immunoglobulin (Ig) classes or impaired vaccine response. Recurrent infections are the predominant presenting symptoms, but autoimmune disorders are also frequent. Onset of symptoms is often after the age of six. Screening for PAD with measurement of the levels of serum IgG, IgM, and IgA is simple and can be done in general practice. Replacement therapy with Ig is the cornerstone in treatment of PAD and reduces the frequency of infections and mortality.

Flow Cytometry Assays in Primary Immunodeficiency Diseases

Inborn errors of immunity are the cause of the primary immunodeficiency diseases, an extremely diverse group of genetic defects that are inherited in Mendelian fashion and result in the impairment of development and/or function of key components of the immune system. Since the last publication of this chapter in 2011, there have been approximately 100 new primary immunodeficiency diseases officially classified by the "Expert Committee for Primary Immunodeficiency" who met in 2015 and the numbers will continue to rise with the continued evolution and widespread adoption of genomic technologies. The ultimate diagnostic modality involves the identification of a mutation in a gene whose product is known to be involved in immunity. DNA sequencing is however still a rather time-consuming technology. Flow cytometry applications have evolved that are rapid, specific, and relatively inexpensive to screen for abnormalities associated with primary immunodeficiency diseases. The numerous flow cytometry procedures that have been developed to detect abnormalities in peripheral blood cells of primary immunodeficiency patients can barely be covered in an entire book, let alone one chapter. Instead of attempting to cover each disease with a specific assay or test, we will review four procedures each covering one of the three following broad forms of immune abnormalities observed in primary immunodeficiency, i.e., immune subset abnormalities, immune marker abnormalities, and immune function abnormalities.

Sublethal Total Body Irradiation Causes Long-Term Deficits in Thymus Function by Reducing Lymphoid Progenitors

Total body irradiation (TBI) damages hematopoietic cells in the bone marrow and thymus; however, the long-term effects of irradiation with aging remain unclear. In this study, we found that the impact of radiation on thymopoiesis in mice varied by sex and dose but, overall, thymopoiesis remained suppressed for ≥12 mo after a single exposure. Male and female mice showed a long-term dose-dependent reduction in thymic cKit⁺ lymphoid progenitors that was maintained throughout life. Damage to hematopoietic stem cells (HSCs) in the bone marrow was dose dependent, with as little as 0.5 Gy causing a significant long-term reduction. In addition, the potential for T lineage commitment was radiation sensitive with aging. Overall, the impact of irradiation on the hematopoietic lineage was more severe in females. In contrast, the rate of decline in thymic epithelial cell numbers with age was radiation-sensitive only in males, and other characteristics including Ccl25 transcription were unaffected. Taken together, these data suggest that long-term suppression of thymopoiesis after sublethal irradiation was primarily due to fewer progenitors in the BM combined with reduced potential for T lineage commitment. A single irradiation dose also caused synchronization of thymopoiesis, with a periodic thymocyte differentiation profile persisting for at least 12 mo postirradiation. This study suggests that the number and capability of HSCs for T cell production can be dramatically and permanently damaged after a single relatively low TBI dose, accelerating aging-associated thymic involution. Our findings may impact evaluation and therapeutic intervention of human TBI events.

Primary intestinal lymphangiectasia in an elderly female patient: A case report on a rare cause of secondary immunodeficiency

Protein loss via the gut can be caused by a number of gastrointestinal disorders, among which intestinal lymphangiectasia has been described to not only lead to a loss of proteins but also to a loss of lymphocytes, resembling secondary immunodeficiency. We are reporting on a 75-year-old female patient who came to our hospital because of a minor stroke. She had no history of serious infections. During the diagnostic work-up, we detected an apparent immunodeficiency syndrome associated with primary intestinal lymphangiectasia. Trying to characterize the alterations of the immune system, we not only found hypogammaglobulinemia and lymphopenia primarily affecting CD4+, and also CD8+ T cells, but also marked hypocomplementemia affecting levels of complement C4, C2, and C3. The loss of components of the immune system most likely was due to a chronic loss of immune cells and proteins via the intestinal lymphangiectasia, with levels of complement components following the pattern of protein electrophoresis. Thus, intestinal lymphangiectasia should not only be considered as a potential cause of secondary immune defects in an elderly patient, but can also be associated with additional hypocomplementemia.

[Thymoma with immunodeficiency/Good syndrome associated with myasthenia gravis]

Good syndrome is a rare condition in which thymoma is associated with hypogammaglobulinemia; it is characterized by repeated respiratory or systemic infections caused by bacteria, viruses, and fungi, as well as with various autoimmune disorders such as pure red cell aplasia. A 65-year-old woman was admitted to our hospital with ptosis and abdominal muscle weakness. Based on the presence of anti-acetylcholine receptor (Ach-R) antibodies, she was diagnosed with myasthenia gravis (MG). At that time, invasive thymoma of Masaoka stage IVa was also detected. Regression of thymoma and clinical remission of MG was achieved by chemotherapy followed by high-dose corticosteroid. However, several months later, the patient started developing repeated bacterial respiratory tract infections, cytomegalovirus infections, and esophageal and systemic candidiasis. Laboratory tests revealed a marked decrease of serum gamma-globulin levels (IgG 586 mg/dl, IgA 32 mg/dl, IgM 29 mg/dl) and severe reduction in the B cells ratio, as well as a decrease in the CD4+CD25+T cell to CD4+CD25-T cell ratio indicative of deregulation of CD4+T cell activation. These results suggested that the patient impaired humoral and cell-mediated immune responses. We continued the treatment with antibiotics and regular immunoglobulin supplementation through intravenous injections. Although autoimmune disorders are often observed in Good syndrome, the association with MG is quite rare. The case report is followed by the review of literature.

Diffuse Nodular Lymphoid Hyperplasia of the Intestine Caused by Common Variable Immunodeficiency and Refractory Giardiasis

Diffuse nodular lymphoid hyperplasia of the gastrointestinal tract is a rare disease characterized by numerous small polypoid nodules in the small intestine, large intestine, or both. It is associated with immunodeficiency and infection, such as Giardia lamblia and Helicobacter pylori. Although diffuse nodular lymphoid hyperplasia associated with common variable immunodeficiency (CVID) and giardiasis is already known, a few studies have reported a regression of the lymphoid nodules after the eradication of infection. We herein describe a case of diffuse nodular lymphoid hyperplasia of the intestine associated with CVID and refractory giardiasis that markedly improved after successfully treating giardiasis.

Secondary antibody deficiency - causes and approach to diagnosis

Antibody deficiencies can occur in the context of primary disorders due to inherited genetic defects; however, secondary immune disorders are far more prevalent and can be caused by various diseases and their treatment, certain medications and surgical procedures. Immunoglobulin replacement therapy has been shown to be effective in reducing infections, morbidity and mortality in primary antibody deficiencies but secondary antibody deficiencies are in general poorly defined and there are no guidelines for the management of patients with this condition. Clinical decisions are based on experience from primary antibody deficiencies. Both primary and secondary antibody deficiencies can be associated with infections, immune dysregulation and end-organ damage, causing significant morbidity and mortality. Therefore, it is important to diagnose and treat these patients promptly to minimise adverse effects and improve quality of life. We focus on secondary antibody deficiency and describe the causes, diagnosis and treatment of this disorder.

Immunodeficiency in the lupus clinic

Systemic lupus erythematous (SLE) and immunodeficiency are linked in various ways. For example, rare genetic complement deficiencies can pre-dispose to developing SLE, whilst some treatments for SLE can cause secondary immunodeficiencies. Various case reports describe SLE patients who have concomitant or later develop antibody deficiency, possibly related to immunosuppressive treatment, or possibly related to the lupus itself. Other components of the immune system, innate and adaptive may also be affected. Immunosuppressive treatment may also cause infections in the absence of defects on routine immunological testing. It is important for the clinician to be aware of the associations between SLE and immunodeficiency to ensure optimal investigation and management. This review focuses on aspects of humoral and cellular immunity, and their association with SLE.

Autoimmunity and Primary Immunodeficiency Disorders

Advances in DNA sequencing technologies have led to a quickening in the pace at which new genetic immunodeficiency disorders have been identified. Among the newly identified defects are a number of disorders that present primarily with autoimmunity as opposed to recurrent infections. These "immune dysregulation" disorders have begun to cluster together to form an increased understanding of some of the basic molecular mechanisms that underlie the establishment and maintenance of immune tolerance and the development of autoimmunity. This review will present three major themes that have emerged in our understanding of the mechanisms that underlie autoimmunity and immune dysregulation in humans.

Treating Immunodeficiency through HSC Gene Therapy

Haematopoietic stem cell (HSC) gene therapy has been successfully employed as a therapeutic option to treat specific inherited immune deficiencies, including severe combined immune deficiencies (SCID) over the past two decades. Initial clinical trials using first-generation gamma-retroviral vectors to transfer corrective DNA demonstrated clinical benefit for patients, but were associated with leukemogenesis in a number of cases. Safer vectors have since been developed, affording comparable efficacy with an improved biosafety profile. These vectors are now in Phase I/II clinical trials for a number of immune disorders with more preclinical studies underway. Targeted gene editing allowing precise DNA correction via platforms such as ZFNs, TALENs and CRISPR/Cas9 may now offer promising strategies to improve the safety and efficacy of gene therapy in the future.

[AUTOIMMUNITY AND IMMUNODEFICIENCIES]

Autoimmune diseases and primary immunodeficiencies share a common pathogenesis characterized by dysregulation of immunity. Although most autoimmune diseases show a polygenic inheritance pattern, it has been shown that monogenic defects of various immune system components could lead to autoimmunity as well. These findings have opened a new pathway for understanding the development of autoimmune diseases and the overlap between immunodeficiency and autoimmunity. Th e mechanism of how a single gene defect leads to autoimmunity is not completely known. The purpose of this clinically-oriented review is to describe the incidence, clinical presentation, and possible mechanisms of autoimmunity in patients with primary immunodeficiencies relevant to rheumatologists.

Morphology and Immunohistochemical Phenotype of the Thymus in Secondary Immunodeficiency

The thymus of outbred male rats 5 months after splenectomy (experimental secondary immunodeficiency) was studied by common histological and immunohistochemical methods using monoclonal and polyclonal antibodies to CD3, CD30, CD68, synaptophysin, to S100, p53, bcl-2, and Ki-67 proteins. Removal of the spleen led to acute involution of the thymic parenchyma, which was replaced by the adipose tissue and was associated with restructuring of the thymopoietic and nonthymopoietic components of the gland, changes in cellular composition and antigenic phenotype of the lobular cortical and medullary matter, and by reduction of cell proliferation.

Primary Immunodeficiency Masquerading as Allergic Disease

Primary immune deficiencies (PIDs) are an uncommon heterogeneous group of diseases that result from fundamental defects in the proteins and cells that enable specific immune responses. Common allergic reactions (eczema, allergic rhinitis, asthma, and food allergies) are exaggerated immune responses that may be manifestations of an underlying PID. Early diagnosis and treatment has significant bearing on outcome. Immune suppression with systemic corticosteroids in these immune compromised individuals can lead to life threatening dissemination of infections.

Abdominal Distension and Escherichia coli Peritonitis in Mice Lacking Myeloid Differentiation Factor 88

Here we describe the gross and microscopic findings of naturally occurring, β-hemolytic Escherichia coli peritonitis in B6.129-Myd88(tm1Aki) male and female mice. Over approximately 5 mo, 10 homozygous mutant mice deficient in myeloid differentiation factor 88 (C57BL/6 strain; male and female) that had not been used in research protocols developed rapid-onset abdominal swelling associated with copious viscous ascites. Each mouse developed an anterior peritonitis, primarily involving the parietal peritoneum and the visceral surface of the spleen, liver, diaphragm, and stomach. Inflammation was confined to the organ surfaces, with no indication of septicemia or grossly apparent gastrointestinal perforation or other tissue compromise that would initiate peritonitis. Peritonitis was likely attributable to compromised antibacterial innate immunity; cohoused, similarly immunodeficient littermates did not develop similar clinical signs. An unusual finding in all cases was mesothelial cell hyperplasia and hypertrophy. Although the underlying innate immune deficiency accounts for much of the observed pathology, the remarkable mesothelial cell morphology and the episodic nature of the peritonitis in some littermates and not others remain unexplained.

The immunology of Epstein-Barr virus-induced disease

Epstein-Barr virus (EBV) is usually acquired silently early in life and carried thereafter as an asymptomatic infection of the B lymphoid system. However, many circumstances disturb the delicate EBV-host balance and cause the virus to display its pathogenic potential. Thus, primary infection in adolescence can manifest as infectious mononucleosis (IM), as a fatal illness that magnifies the immunopathology of IM in boys with the X-linked lymphoproliferative disease trait, and as a chronic active disease leading to life-threatening hemophagocytosis in rare cases of T or natural killer (NK) cell infection. Patients with primary immunodeficiencies affecting the NK and/or T cell systems, as well as immunosuppressed transplant recipients, handle EBV infections poorly, and many are at increased risk of virus-driven B-lymphoproliferative disease. By contrast, a range of other EBV-positive malignancies of lymphoid or epithelial origin arise in individuals with seemingly intact immune systems through mechanisms that remain to be understood.

[CLINICAL AND DIAGNOSTIC SIGNIFICANCE OF IMMUNOGLOBULIN G SUBCLASSES IN IMMUNODEFICIENCY VERIFICATION]

In general practice of clinical immunologists must be use the detection of immunoglobulin G subclasses in cases with symptoms of recurrent and chronic infectious diseases with normal serum IgG. Thus, these patients are not examined and they are under treatment. Over the years, these patients has a sharp decrease in IgG subclasses, which is accompanied by a long course of various infectious processes and complications. Therefore; early diagnosis, early treatment and prevention of complications immunodeficiency knowledge-based clinical immunologists and general practitioners of modern diagnostic methods.

The immune system and aging: a review

Abstract The concept of immunosenescence reflects age-related changes in immune responses, both cellular and serological, affecting the process of generating specific responses to foreign and self-antigens. The decline of the immune system with age is reflected in the increased susceptibility to infectious diseases, poorer response to vaccination, increased prevalence of cancer, autoimmune and other chronic diseases. Both innate and adaptive immune responses are affected by the aging process; however, the adaptive response seems to be more affected by the age-related changes in the immune system. Additionally, aged individuals tend to present a chronic low-grade inflammatory state that has been implicated in the pathogenesis of many age-related diseases (atherosclerosis, Alzheimer's disease, osteoporosis and diabetes). However, some individuals arrive to advanced ages without any major health problems, referred to as healthy aging. The immune system dysfunction seems to be somehow mitigated in this population, probably due to genetic and environmental factors yet to be described. In this review, an attempt is made to summarize the current knowledge on how the immune system is affected by the aging process.

Occurrence of intestinal microsporidia in immunodeficient patients in Poland

Microsporidial infections may be asymptomatic in immunocompetent hosts, but can be severe and disseminated in HIV/AIDS patients, children, the elderly, or in immunocompromised individuals, including those with primary or medically-induced immunodeficiencies. 209 faecal samples were collected from 80 clinical patients, with or without abdominal symptoms, and tested for the presence of the parasites. Microsporidia were found in 10 of the 80 patients (12.5%) using trichrom staining of faecal smears and/or PCR. Encephalitozoon intestinalis and 1 unidentified species were identified in 2 of the 32 children with primary immunodeficiencies (6%), presenting with diarrhoea, including one co-infection with Cryptosporidium meleagridis. In the group of patients with medically-induced immunosuppression (transplant recipients), 8 of the 48 patients (17%) were tested positive for microsporidia. Thus, these pathogens should be taken into account when the other etiological agents cannot be found in diarrheic patients with PIDs or undergoing immunosuppressive treatment before or after transplantation. This article presents the results of the first epidemiological study on the occurrence and prevalence of microsporidia in patients with primary and secondary immunodeficiency in Poland.

Acute neonatal infections 'lock-in' a suboptimal CD8+ T cell repertoire with impaired recall responses

Microbial infection during various stages of human development produces widely different clinical outcomes, yet the links between age-related changes in the immune compartment and functional immunity remain unclear. The ability of the immune system to respond to specific antigens and mediate protection in early life is closely correlated with the level of diversification of lymphocyte antigen receptors. We have previously shown that the neonatal primary CD8+ T cell response to replication competent virus is significantly constricted compared to the adult response. In the present study, we have analyzed the subsequent formation of neonatal memory CD8+ T cells and their response to secondary infectious challenge. In particular, we asked whether the less diverse CD8+ T cell clonotypes that are elicited by neonatal vaccination with replication competent virus are ‘locked-in’ to the adult memory T cell, and thus may compromise the strength of adult immunity. Here we report that neonatal memory CD8+ T cells mediate poor recall responses compared to adults and are comprised of a repertoire of lower avidity T cells. During a later infectious challenge the neonatal memory CD8+ T cells compete poorly with the fully diverse repertoire of naïve adult CD8+ T cells and are outgrown by the adult primary response. This has important implications for the timing of vaccination in early life.

Newborns typically have a heightened sensitivity to infectious diseases, the reasons for which are not yet well understood. One contributing factor is the limited diversity of lymphocyte receptors early in life to recognize antigen and control infection. We have previously shown that antigen-specific CD8+ T cell repertoires are significantly constricted in neonates compared with adults. In this study, we addressed the question of whether the developmental stage of the host at the time of vaccination influences the composition of the memory CD8⁺ T cell repertoire and its ability to mount a robust response to subsequent infections. We observed that the antigen-specific T cell repertoires elicited in the context of an acute neonatal infection, that are less diverse and comprised of lower-avidity T cells, are partially ‘locked-in’ to the adult memory T cell repertoire. However, in the face of a secondary infectious challenge, naïve adult T cells outcompete the lower avidity neonatal memory T cells and raise the diversity of the overall CD8⁺ T cell response. These results have potential implications for the design of vaccines to be administered in early life.

Hyposplenism: A comprehensive review. Part II: Clinical manifestations, diagnosis, and management

In the first part of this review, we described the physiological basis of splenic function and hypofunction. We also described the wide spectrum of diseases that can result in functional hyposplenism. In the second part of this review, we will be discussing the clinical picture, including complications, diagnostic methods, and management of hyposplenism.

Antibody deficiency in patients with ataxia telangiectasia is caused by disturbed B- and T-cell homeostasis and reduced immune repertoire diversity

BACKGROUND

Ataxia telangiectasia (AT) is a multisystem DNA-repair disorder caused by mutations in the ataxia telangiectasia mutated (ATM) gene. Patients with AT have reduced B- and T-cell numbers and a highly variable immunodeficiency. ATM is important for V(D)J recombination and immunoglobulin class-switch recombination (CSR); however, little is known about the mechanisms resulting in antibody deficiency severity.

OBJECTIVE

We sought to examine the immunologic mechanisms responsible for antibody deficiency heterogeneity in patients with AT.

METHODS

In this study we included patients with classical AT plus early-onset hypogammaglobulinemia (n = 3), classical AT (n = 8), and variant AT (late onset, n = 4). We studied peripheral B- and T-cell subsets, B-cell subset replication history, somatic hypermutation frequencies, CSR patterns, B-cell repertoire, and ATM kinase activity.

RESULTS

Patients with classical AT lacked ATM kinase activity, whereas patients with variant AT showed residual function. Most patients had disturbed naive B-cell and T-cell homeostasis, as evidenced by low cell numbers, increased proliferation, a large proportion CD21(low)CD38(low) anergic B cells, and decreased antigen receptor repertoire diversity. Impaired formation of T cell-dependent memory B cells was predominantly found in patients with AT plus hypogammaglobulinemia. These patients had extremely low naive CD4(+) T-cell counts, which were more severely reduced compared with those seen in patients with classical AT without hypogammaglobulinemia. Finally, AT deficiency resulted in defective CSR to distal constant regions that might reflect an impaired ability of B cells to undergo multiple germinal center reactions.

CONCLUSION

The severity of the antibody deficiency in patients with AT correlates with disturbances in B- and T-cell homeostasis resulting in reduced immune repertoire diversity, which consequently affects the chance of successful antigen-dependent cognate B-T interaction.

[Immune reactivity in workers engaged in cement production]

The authors studied immune state of workers engaged in cement production. Ambivalent changes of immune parameters in apparently healthy workers depict various stages of adaptational protective reactions in body system. The studies support gradual changes in immune system under continued influence of occupational factors.

The burden of drinking water-associated cryptosporidiosis in China: the large contribution of the immunodeficient population identified by quantitative microbial risk assessment

A comprehensive quantitative microbial risk assessment (QMRA) of Cryptosporidium infection, considering pathogen removal efficiency, different exposure pathways and different susceptible subpopulations, was performed based on the result of a survey of source water from 66 waterworks in 33 major cities across China. The Cryptosporidium concentrations in source water were 0-6 oocysts/10 L, with a mean value of 0.7 oocysts/10 L. The annual diarrhea morbidity caused by Cryptosporidium in drinking water was estimated to be 2701 (95% confidence interval (CI): 138-9381) cases per 100,000 immunodeficient persons and 148 (95% CI: 1-603) cases per 100,000 immunocompetent persons, giving an overall rate of 149.0 (95% CI: 1.3-606.4) cases per 100,000 population. The cryptosporidiosis burden associated with drinking water treated with the conventional process was calculated to be 8.31 × 10(-6) (95% CI: 0.34-30.93 × 10(-6)) disability-adjusted life years (DALYs) per person per year, which was higher than the reference risk level suggested by the World Health Organization (WHO), but lower than that suggested by the United States Environmental Protection Agency (USEPA). Sixty-six percent of the total health burden due to cryptosporidiosis that occurred in the immunodeficient subpopulation, and 90% of the total DALYs was attributed to adults aged 15-59 years. The sensitivity analysis highlighted the great importance of stability of the treatment process and the importance of watershed protection. The results of this study will be useful in better evaluating and reducing the burden of Cryptosporidium infection.

Chapter 27: Approach to primary immunodeficiency

Primary immunodeficiency diseases (PID) are inherited defects of the innate or adaptive arms of the immune system that lead to an increase in the incidence, frequency, or severity of infections. There may be defects in the adaptive arm of the immune system that include combined immunodeficiency and antibody deficiency syndromes or by abnormalities in innate immunity such as disorders of phagocytes, the complement pathway, or Toll-Like receptor (TLR) mediated signaling. Recurrent sinopulmonary infections with encapsulated bacteria such as Haemophilus influenza type B or Streptococcus pneumoniae may be characteristic of an IgG antibody deficiency or dysfunction. Frequent viral, fungal, or protozoal infections may suggest T lymphocyte dysfunction. Multiple staphylococcal skin infections and fungal infections may imply neutrophil dysfunction or the hyper-IgE syndrome, and recurrent neisserial infection is a characteristic manifestation of late complement component (C5-9, or the membrane attack complex) defects. Recurrent viral or pyogenic bacterial infections often without the presence of a significant inflammatory response suggest a defect in TLR signaling. Mycobacterial infections are characteristic of defects in interleukin (IL)-12, interferon (IFN) gamma, or their receptors. Screening of newborns for T-cell lymphopenia using a polymerase chain reaction to amplify T-cell receptor excision circles (TRECs), which are formed when a T cell rearranges the variable region of its receptor, serves as a surrogate for newly synthesized naïve T cells. Because of very low numbers of TRECs, severe combined immunodeficiency, DiGeorge syndrome, and other causes of T-cell lymphopenia have been identified in newborns.

NCI, NHLBI/PBMTC first international conference on late effects after pediatric hematopoietic cell transplantation: persistent immune deficiency in pediatric transplant survivors

Defective immune reconstitution is a major barrier to successful hematopoietic cell transplantation (HCT), and has important implications in the pediatric population. There are many factors that affect immune recovery, including stem cell source and graft-versus-host disease (GVHD). Complete assessment of immune recovery, including T and B lymphocyte evaluation, innate immunity, and response to neoantigens, may provide insight as to infection risk and optimal time for immunizations. The increasing use of cord blood grafts requires additional study regarding early reconstitution and impact upon survival. Immunization schedules may require modification based upon stem cell source and immune reconstitution, and this is of particular importance as many children have been incompletely immunized, or not at all, before school entry. Additional studies are needed in children post-HCT to evaluate the impact of differing stem cell sources upon immune reconstitution, infectious risks, and immunization responses.

Impaired immune function in children with Fanconi anaemia

Fanconi anaemia is an autosomal recessive or X-linked disease characterized by progressive bone marrow failure, variable congenital abnormalities and a predisposition to malignancy. Reports of immune function in this population are limited, and include only specific areas of immune performance, showing variable defects. We report a cross-sectional immunological assessment in 10 children with FA. Absolute numbers of B cells and natural killer (NK) cells were reduced compared to controls (P = 0·048 and P = 0·0002, respectively), while absolute number of T cells were within normal range. Perforin and granzyme content of NK cells was reduced (P < 0·00001 and P = 0·0057, respectively) along with the NK cell cytotoxicity (P < 0·001). Antigen proliferation in response to tetanus was decreased (P = 0·008) while responses to candida and phytohaemagglutinin were not. Cytotoxic T cell function was also reduced (P < 0·0001). Immunoglobulin G levels were normal in those evaluated. Our series represents the first attempt at a comprehensive quantitative and functional evaluation of immune function in this rare group of patients and demonstrates a significant deficit in the NK cell compartment, a novel quantitative B cell defect, along with abnormal cytotoxic function. These findings may be especially relevant in this patient population with known predisposition to DNA damage and malignancy.

Nutritionally acquired immune deficiency syndromes (NAIDS): common but often not diagnosed early

It has been the perception in some pacific island countries that the textbook presentation of kwashiorkor has decreased in incidence possibly due to improved public health services and economic development of the country. However, the diagnosis and treatment is nonetheless crucial to child survival. This paper discusses the clinical courses of 2 children with kwashiorkor whose presentation were not of that taught to medical students or even junior doctors. Their presentation together with their subsequent nutritionally acquired immune deficiency syndrome (NAIDS) is illustrated to raise awareness of the complexities in diagnosis and management of such patients.

[Antibody deficiencies. A survey from three Clinical Immunology Centers for adults in Buenos Aires city]

Antibody deficiency (AD) comprises a group of diseases characterized by the inability to develop an effective antibody mediated immune response. These patients suffer mainly of encapsulated extracellular bacterial infections of the respiratory tract. The aim of our study was to describe the clinical characteristics of 128 patients with suspected or confirmed AD who were referred to 3 immunodeficiency centers for adults, from June 2004 to December 2009. Three of these patients (2.3%) consulted for recurrent infections only once, without sufficient data for a proper classification, and were excluded. Of the remaining 125 patients, in 21 (16.8%) AD was excluded, 8 cases (6.4%) were diagnosed with secondary antibody immunodeficiency (SAD) and 96 (76.8%) with primary antibody immunodeficiency (PAD). SAD causes were: one renal failure, one phenytoin use, two monoclonal gammopathy and four B cell lymphoma. The causes of these 96 PAD were: 57 common variable immunodeficiency, 12 X-linked agammaglobulinaemia, 10 selective IgA deficiency, seven IgG1 deficiency, three hyper-IgM syndrome, three IgM deficiency, two X-linked proliferative syndrome, one Good syndrome and one antibody functional deficiency. Sixty-seven patients were in follow up at the time of completion of the study, 25 of them were on follow up at the beginning of the study. Among the 58 patients with indication of gamma globulin replacement therapy, 54 were in treatment at the end of the study. In four patients the initial diagnosis of PAD was not confirmed.

Immune deficiency caused by impaired expression of nuclear factor-kappaB essential modifier (NEMO) because of a mutation in the 5' untranslated region of the NEMO gene

BACKGROUND

Nuclear factor-kappaB (NF-kappaB) is a key transcription factor that regulates both innate and adaptive immunity as well as ectodermal development. Mutations in the coding region of the IkappaB kinase gamma/NF-kappaB essential modifier (NEMO) gene cause X-linked ectodermal dysplasia with immunodeficiency.

OBJECTIVE

To determine the genetic cause of recurrent sinopulmonary infections and dysgammaglobulinemia in a patient with a normal NEMO coding sequence and his affected brother.

METHODS

TNF-alpha and IFN-alpha production in response to Toll-like receptor (TLR) stimulation was analyzed by ELISA, NEMO mRNA levels were measured by quantitative PCR, and NEMO protein expression was measured by Western blotting. NF-kappaB activation was assessed by nuclear translocation of p65 and luciferase reporter gene assays.

RESULTS

TLR-induced TNF-alpha and IFN-alpha production by PBMCs was impaired in the patient and his brother. Sequencing of the patient's NEMO gene revealed a novel mutation in the 5' untranslated region, which was also present in the brother, resulting in abnormally spliced transcripts and a 4-fold reduction in mRNA levels. NEMO protein levels in EBV transformed B cells and fibroblasts from the index patient were 8-fold lower than normal controls. NF-kappaB p65 nuclear translocation in the patient's EBV B cells after TLR7 ligation was defective. NF-kappaB-dependent luciferase gene expression in IL-1-stimulated fibroblasts from the patient was impaired.

CONCLUSION

This is the first description of immune deficiency resulting from low expression of a normal NEMO protein.