Respiratory Complications in Patients with Hyper IgM Syndrome

Elevated levels of enteric IgA in an unimmunised mouse model of Hyper IgM syndrome derived from gut-associated secondary lymph organs even in the absence of germinal centres

Introduction

Patients with Human Hyper IgM syndromes (HIGM) developed pulmonary and gastrointestinal infections since infancy and most patients have mutations in the CD40 ligand (CD40L) gene. Most HIGM patients compared to healthy subjects have higher/similar IgM and lower IgG, and IgA serum concentrations but gut antibody concentrations are unknown. CD40L on activated T-cells interacts with CD40 on B-cells, essential for the formation of germinal centres (GCs) inside secondary lymphoid organs (SLOs), where high-affinity antibodies, long-lived antibody-secreting plasma cells, and memory B-cells, are produced. C57BL6-CD40 ligand deficient mice (C57BL6-cd40l ^-/-), are a model of HIGM, because serum immunoglobulin concentrations parallel levels observed in HIGM patients and have higher faecal IgA concentrations. In mice, TGFβ and other cytokines induce IgA production.

Aims

To compare and evaluate B-cell populations and IgA-producing plasma cells in peritoneal lavage, non-gut-associated SLOs, spleen/inguinal lymph nodes (ILN), and gut-associated SLOs, mesenteric lymph nodes (MLN)/Peyer´s patches (PP) of unimmunised C57BL6-cd40l ^-/- and C57BL6-wild-type (WT) mice.

Material and methods

Peritoneal lavages, spleens, ILN, MLN, and PP from 8-10 weeks old C57BL6-cd40l ^-/- and WT mice, were obtained. Organ cryosections were analysed by immunofluorescence and B-cell populations and IgA-positive plasma cell suspensions by flow cytometry.

Results

In unimmunised WT mice, GCs were only observed in the gut-associated SLOs, but GCs were absent in all C57BL6-cd40l ^-/- SLOs. PP and MLN of C57BL6-cd40l ^-/- mice exhibited a significantly higher number of IgA-producing cells than WT mice. In the spleen and ILN of C57BL6-cd40l^{- /-} mice IgA-producing cells significantly decreased, while IgM-positive plasma cells increased. C57BL6-cd40l ^-/- B-1 cells were more abundant in all analysed SLOs, whereas in WT mice most B-1 cells were contained within the peritoneal cavity. C57BL6-cd40l ^-/- B-cells in MLN expressed a higher TGFβ receptor-1 than WT mice. Mouse strains small intestine microvilli (MV), have a similar frequency of IgA-positive cells.

Discussion

Together our results confirm the role of PP and MLN as gut inductive sites, whose characteristic features are to initiate an IgA preferential immune response production in these anatomical sites even in the absence of GCs. IgA antibodies play a pivotal role in neutralising, eliminating, and regulating potential pathogens and microorganisms in the gut.

Respiratory infections in X-linked hyper-IgM syndrome with CD40LG mutation: a case series of seven children in China

BACKGROUND

X-linked hyper-immunoglobulin M (XHIGM), a primary immunodeficiency syndrome caused by mutations in the CD40 ligand gene(CD40LG), presents with recurrent respiratory infections in pediatric patients. We aimed to evaluate the spectrum of clinical features and respiratory pathogens in pediatric patients with XHIGM in China.

METHODS

We retrospectively reviewed seven pediatric patients who were diagnosed with XHIGM and received follow-up treatment at the Guangzhou Women and Children's Medical Center between January 2010 and January 2021. We determined their clinical characteristics, causative pathogens, and prognosis by performing peripheral immunological and genetic tests.

RESULTS

There were seven boys with age ranging from 4-20 months (median age, 13 months). Four of the seven respiratory infections were caused by Talaromyces marneffei(T. marneffei). Two patients had viral infections caused by cytomegalovirus (CMV) and human adenovirus respectively. One patient had a mixed infection caused by Pneumocystis carinii and CMV. Except for one child who died of respiratory failure, one patient received hematopoietic stem cell transplantation (HSCT) and recovered well, the other five patients survived with regular infusions of intravenous immunoglobulin (IVIg) during the follow-up period. Six patients had reduced antibody levels, especially IgG, IgA, and IgE levels. Increased serum IgM levels were detected in four cases, and three cases presented normal IgM levels at onset. All children were diagnosed with XHIGM with CD40LG variation. Three novel mutations were identified in the present study.

CONCLUSIONS

Our study suggests that respiratory infections usually begin within 2 years old, fungi and viruses are important pathogens causing respiratory infections in children with XHIGM. In endemic areas, T. marneffei is the common pathogen of respiratory tract infection in children with the disease.

Somatic hypermutation defects in two adult hyper immunoglobulin M patients

Hyper immunoglobulin M (HIGM) syndrome is a rare disorder of the immune system with impaired antibody functions. The clinical picture of the patients varies according to the underlying genetic variation. In this study, we identified two novel variants in AID and UNG genes, which are associated with autosomal recessive type HIGM, by targeted next-generation sequencing (NGS) panel. A biallelic 11 base pair deletion (c.278_288delATGTGGCCGAC) in the coding sequence of activation-induced cytidine deaminase (AID) gene was identified in a 36-year-old patient. Biallelic two base pair insertion in exon 7 of uracil nucleoside glycosylase (UNG) gene (c.924_925insGG) was identified in a 40-year-old patient. Both variants were confirmed by Sanger sequencing. HIGM, like many of the other primary immunodeficiencies, is a rare and difficult-to-diagnose entity with heterogeneous clinical phenotypes. It should be suspected in patients with a history of early-onset recurrent respiratory infections, enlarged lymph nodes, and autoimmune disorders. There might be a delay in diagnosis until adulthood especially in subtle cases or if HIGM is not included in the differential diagnosis due lacking of awareness. In this regard, genetic testing with NGS-based diagnostic panels provide a rapid and reasonable tool for the molecular diagnosis of patients with immunodeficiencies and hence, decrease the time to diagnose and prevent infection-related complications associated with increased morbidity and mortality.

Imaging Features of Primary Immunodeficiency Disorders

Primary immunodeficiency disorders (PIDs), which are humoral, combined, and innate defects of the immune system, are relatively uncommon and may go undiagnosed in patients experiencing recurrent infections, resulting in increased morbidity and mortality. PIDs are clinically characterized by a broad spectrum of disorders, including repeated infections, autoimmune disorders, lymphoproliferative diseases, congenital anomalies, and increased risk of malignancy. Cardiothoracic imaging plays a crucial role in the diagnosis of PIDs owing to the high rates of repeated respiratory infections leading to bronchiectasis and other forms of chronic lung disease. Although PIDs as a group may seem similar in terms of radiologic features and clinical manifestations, there are specific entities that are pertinent to each PID on an individual level. For example, patients with common variable immunodeficiency may develop a unique granulomatous lymphocytic interstitial lung disease, and Good syndrome is associated with thymoma. Familiarity with the imaging characteristics of these disorders may expedite diagnosis and prognostication, and better direct therapy. Reviewing the thoracic manifestations of all PIDs is beyond the scope of this article; thus, the focus herein is on discussing the thoracic manifestations of the most common PIDs and their imaging features. © RSNA, 2021An earlier incorrect version appeared online. This article was corrected on March 25, 2021.

Comprehensive assessment of respiratory complications in patients with common variable immunodeficiency

BACKGROUND

Common variable immunodeficiency (CVID) is a heterogeneous group of disorders, characterized by recurrent upper and lower respiratory tract infections and some noninfectious clinical complications.

OBJECTIVE

To provide a detailed evaluation of respiratory presentations and complications in a cohort of Iranian patients with CVID.

METHODS

A retrospective cohort study was conducted on 245 CVID patients who were recorded in the Iranian primary immunodeficiency disorders registry network. Respiratory manifestations were evaluated by reviewing clinical hospital records, immunologic findings, pulmonary function tests (PFT), and high-resolution computed tomography (HRCT) scans.

RESULTS

Most of the patients (n = 208, 85.2%) had experienced at least 1 episode of acute respiratory manifestation, and pneumonia was observed in 31.6 % (n = 77) of cases as a first disease manifestation. During the follow-up, pneumonia, sinusitis, and otitis media were documented in 166 (68.6%), 125 (51.2%), and 103 (42.6%) cases, respectively. Abnormal PFT measurements were documented in 53.8% of patients. Among these patients, 21.5% showed restrictive changes, whereas 18.4% of patients showed an obstructive pattern. Bronchiectasis was the most frequent radiological finding, confirmed in 27.2% of patients. Patients with bronchiectasis were older at the time of immunodeficiency diagnosis (P < .001) and had longer diagnosis delay (P < .001) when compared with patients without bronchiectasis.

CONCLUSION

This study highlights the importance of monitoring the respiratory tract system even in asymptomatic patients. Pulmonary function tests and CT scans are the most commonly used techniques aiming to identify these patients early, aiming to reduce the rate of long-term respiratory complications.