Altered distribution of IgG subclasses in aspirin-induced asthma: high IgG4, low IgG1

Local immunoglobulin production in nasal tissues: A key to pathogenesis in chronic rhinosinusitis with nasal polyps and aspirin-exacerbated respiratory disease

OBJECTIVE

Local activation of B cells and antibody production are important for protective and pathogenic immune responses. Furthermore, there is evidence that local activation of B cells and antibody production are important for pathogenesis of chronic rhinosinusitis with nasal polyps (CRSwNP) and a severe subset of CRSwNP, aspirin-exacerbated respiratory disease (AERD). This review summarizes these findings and the potential role of B cells and antibodies in disease pathogenesis.

DATA SOURCES

Published literature from PubMed searches.

STUDY SELECTIONS

Studies relevant to B cell development and the roles of B cells and antibodies in the pathogenesis of CRSwNP and AERD.

RESULTS

Formation of tertiary lymphoid structures plays a key role in the local activation of B cells and antibody production. This process is important for fighting infections, but it also contributes to autoimmune disease. Furthermore, there is evidence to support a role for local B cell activation and antibody production in a variety of allergic diseases. Nasal polyp tissues from patients with CRSwNP and AERD have elevated levels of activated B cell subsets and locally produced antibodies. These locally produced antibodies may contribute to disease pathogenesis in a variety of ways, including activation of innate effector cells, whereas locally activated B cells may contribute to pathogenesis through the activation of T cells.

CONCLUSION

More studies are needed to determine the role of B cells and antibodies in driving disease in these patients. However, targeting the processes that drive local B cell activation and antibody production may provide new therapeutic approaches and could help to reduce chronic inflammation.

IL-5Rα marks nasal polyp IgG4- and IgE-expressing cells in aspirin-exacerbated respiratory disease

BACKGROUND

The cause of severe nasal polyposis in aspirin-exacerbated respiratory disease (AERD) is unknown. Elevated antibody levels have been associated with disease severity in nasal polyps, but upstream drivers of local antibody production in nasal polyps are undetermined.

OBJECTIVE

We sought to identify upstream drivers and phenotypic properties of local antibody-expressing cells in nasal polyps from subjects with AERD.

METHODS

Sinus tissue was obtained from subjects with AERD, chronic rhinosinusitis (CRS) with nasal polyps (CRSwNP), CRS without nasal polyps, and controls without CRS. Tissue antibody levels were quantified via ELISA and immunohistochemistry and were correlated with disease severity. Antibody-expressing cells were profiled with single-cell RNA sequencing, flow cytometry, and immunofluorescence, with IL-5Rα function determined through IL-5 stimulation and subsequent RNA sequencing and quantitative PCR.

RESULTS

Tissue IgE and IgG4 levels were elevated in AERD compared with in controls (P < .01 for IgE and P < .001 for IgG4 vs CRSwNP). Subjects with AERD whose nasal polyps recurred rapidly had higher IgE levels than did subjects with AERD, with slower regrowth (P = .005). Single-cell RNA sequencing revealed increased IL5RA, IGHG4, and IGHE in antibody-expressing cells from patients with AERD compared with antibody-expressing cells from patients with CRSwNP. There were more IL-5Rα⁺ plasma cells in the polyp tissue from those with AERD than in polyp tissue from those with CRSwNP (P = .026). IL-5 stimulation of plasma cells in vitro induced changes in a distinct set of transcripts.

CONCLUSIONS

Our study identifies an increase in antibody-expressing cells in AERD defined by transcript enrichment of IL5RA and IGHG4 or IGHE, with confirmed surface expression of IL-5Rα and functional IL-5 signaling. Tissue IgE and IgG4 levels are elevated in AERD, and higher IgE levels are associated with faster nasal polyp regrowth. Our findings suggest a role for IL-5Rα⁺ antibody-expressing cells in facilitating local antibody production and severe nasal polyps in AERD.

Genetic mechanisms in aspirin-exacerbated respiratory disease

Aspirin-exacerbated respiratory disease (AERD) refers to the development of bronchoconstriction in asthmatics following the exposure to aspirin or other nonsteroidal anti-inflammatory drugs. The key pathogenic mechanisms associated with AERD are the overproduction of cysteinyl leukotrienes (CysLTs) and increased CysLTR1 expression in the airway mucosa and decreased lipoxin and PGE2 synthesis. Genetic studies have suggested a role for variability of genes in disease susceptibility and the response to medication. Potential genetic biomarkers contributing to the AERD phenotype include HLA-DPB1, LTC4S, ALOX5, CYSLT, PGE2, TBXA2R, TBX21, MS4A2, IL10, ACE, IL13, KIF3A, SLC22A2, CEP68, PTGER, and CRTH2 and a four-locus SNP set composed of B2ADR, CCR3, CysLTR1, and FCER1B. Future areas of investigation need to focus on comprehensive approaches to identifying biomarkers for early diagnosis.

Role of Toll-like Receptor 3 Variants in Aspirin-Exacerbated Respiratory Disease

Purpose

Although the mechanism of virus-induced, aspirin-exacerbated respiratory disease (AERD) is not known fully, direct activation of viral components through Toll-like receptor 3 (TLR3) has been suggested. TLR3 recognizes double-stranded RNA (dsRNA), and activates nuclear factor-κB and increases interferon-γ, which signals other cells to induce airway inflammation in asthma. Considering the association of TLR3 in viral infections and AERD, we investigated whether promoter and non-synonymous variants of TLR3 were associated with AERD.

Methods

The three study groups, 203 with AERD, 254 with aspirin-tolerant asthma (ATA), and 274 normal healthy controls (NC) were recruited from Ajou University Hospital, Korea. Two polymorphisms, -299698G>T and 293391G>A [Leu412Phe], were genotyped using primer extension methods.

Results

Genetic associations were examined between two genetic polymorphisms of TLR3 (-299698G>T and 293391G>A [Leu412Phe]) in the three study groups. AERD patients that carried the GG genotype of 293391G>A showed a significantly lower frequency compared with ATA in both co-dominant (P=0.025) and dominant models (P=0.036). Similarly, in the minor allele frequency, the A allele was significantly higher (P=0.023) in AERD compared with ATA for this polymorphism. AERD patients who carried HT2 [GA] showed a significantly higher frequency than other haplotypes in co-dominant (P=0.02) and recessive (P=0.026) models.

Conclusions

Our findings suggest that the -299698G>T and 293391G>A [Leu412Phe] polymorphisms of the TLR3 gene are associated with the AERD phenotype.

Update on recent advances in the management of aspirin exacerbated respiratory disease

Aspirin intolerant asthma (AIA) is frequently characterized as an aspirin (ASA)-exacerbated respiratory disease (AERD). It is a clinical syndrome associated with chronic severe inflammation in the upper and lower airways resulting in chronic rhinitis, sinusitis, recurrent polyposis, and asthma. AERD generally develops secondary to abnormalities in inflammatory mediators and arachidonic acid biosynthesis expression. Upper and lower airway eosinophil infiltration is a key feature of AERD; however, the exact mechanisms of such chronic eosinophilic inflammation are not fully understood. Cysteinyl leukotriene over-production may be a key factor in the induction of eosinophilic activation. Genetic studies have suggested a role for variability of genes in disease susceptibility and response to medication. Potential genetic biomarkers contributing to the AERD phenotype include HLA-DPB1*301, LTC4S, ALOX5, CYSLT, PGE2, TBXA2R, TBX21, MS4A2, IL10 -1082A > G, ACE -262A > T, and CRTH2 -466T > C; the four-locus SNP set was composed of B2ADR 46A > G, CCR3 -520T > G, CysLTR1 -634C > T, and FCER1B -109T > C. Management of AERD is an important issue. Aspirin ingestion may result in significant morbidity and mortality, and patients must be advised regarding aspirin risk. Leukotriene receptor antagonists (LTRA) that inhibit leukotriene pathways have an established role in long-term AERD management and rhinosinusitis. Aspirin desensitization may be required for the relief of upper and lower airway symptoms in AERD patients. Future research should focus on identification of biomarkers for a comprehensive diagnostic approach.

Pathogenesis and management of aspirin-intolerant asthma

In 2-23% of adults with asthma, and rarely in children with asthma, aspirin (acetylsalicylic acid) and non-steroidal anti-inflammatory drugs (NSAIDs) cause asthma exacerbations. Within 3 hours of ingestion of aspirin/NSAIDs, individuals with aspirin-intolerant asthma (AIA) develop bronchoconstriction, often accompanied by rhinorrhea, conjunctival irritation, and scarlet flush. In severe cases, a single therapeutic dose of aspirin/NSAIDs can provoke violent bronchospasm, loss of consciousness, and respiratory arrest. In order to diagnose AIA, oral, inhaled, nasal or intravenous aspirin challenge tests are performed in facilities where experienced physicians are present and emergency treatment is available. The exact differences in the pathogenesis of AIA and other types of asthma are not fully understood. The interference of aspirin/NSAIDs with arachidonic acid metabolism in the lungs plays an important role in the mechanism of AIA; inhibition of cyclo-oxygenase is accompanied by overproduction of cysteinyl leukotrienes (cys-LTs). It has been proposed that overproduction of cys-LTs, together with removal by aspirin/NSAIDs of the 'brake' imposed by the bronchodilator prostaglandin E2, may cause an asthma attack in patients with AIA. Development of a suitable animal model to investigate the pathogenesis of AIA would help to clarify this question. Although it is still controversial whether leukotriene modifiers are more effective in patients with AIA compared with other types of asthma, because LT plays an important role in the pathogenesis of AIA, leukotriene modifiers are the preferred medication for the long-term control of AIA. Add-on efficacy of leukotriene modifiers has been confirmed in patients with AIA already treated with inhaled corticosteroids. However, this does not mean that aspirin/NSAIDs can be safely taken by aspirin-sensitive patients treated with leukotriene modifiers. To prevent attacks of AIA, sensitive patients should avoid the use of aspirin/NSAIDs or use selective cyclo-oxygenase 2 inhibitors when required. When patients with AIA need aspirin for specific situations they should receive aspirin desensitization therapy or treatment with selective cyclo-oxygenase 2 inhibitors.

Specific immunoglobulins to soybean hull allergens in soybean asthma

Soybean asthma, which occurred as an epidemic among patients in Barcelona, Spain, is associated with specific IgE to soybean hull allergens. The purpose of this study was to investigate the possible role of specific IgG, IgG subclasses, IgA, and IgM in the pathogenesis of soybean asthma. We studied 3 groups of subjects from Barcelona: group 1, 12 asthmatic epidemic patients; group 2, 23 asthmatic nonepidemic patients; and group 3, 32 nonallergic subjects. Specific IgE was determined by radioimmunoassay and specific IgG, IgG subclasses (1, 2, 3, and 4), IgA, and IgM by amplified enzyme-linked immunosorbent assay. Cross-inhibition studies were performed for specific IgE and IgG4. We partially characterized the soybean hull allergens that bind specific IgE, IgG, and IgG4 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis/Western blot. Percentage of positive results for the assays of the 8 Igs are as follows: for group 1, 100% (IgE), 75% (IgG), 16.6% (IgG1), 8.3% (IgG2), 0% (IgG3), 66.6% (IgG4), 25% (IgA), and 25% (IgM); for group 2, 4.3% were positive for specific IgE only; and for group 3, 0% (IgE), 0% (IgG), 6.2% (IgG1), 9.4% (IgG2), 9.4% (IgG3), 9.4% (IgG4), 6.2% (IgA), and 6.2% (IgM). The correlation between the specific IgE and the other specific Igs was significant between IgE and IgG4 in group 1 only (r = 0.752, p < 0.01). Cross-inhibition studies demonstrated a higher inhibitory capacity for IgG4 than for IgE. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis/ Western blot demonstrates three low molecular weight protein bands that bind specific IgE, IgG, and IgG4. This study suggests that specific IgG4 to soybean hull allergens plays a role in the pathogenesis of soybean asthma and corroborates the role of specific IgE in the same disease.

Short courses of high-dose inhaled budesonide and serum IgG subclass levels in healthy volunteers

BACKGROUND

The incidence of systemic side effects of inhaled budesonide increases at doses exceeding 2000 micrograms/day.

OBJECTIVE

This study was carried out to investigate whether high-dose inhaled budesonide affects serum IgG subclass concentrations in healthy adult volunteers.

METHODS

Two groups of 10 subjects each inhaled 2.4 mg of budesonide per day in a double-blind, crossover study of morning (8:00 AM and noon, group A) and diurnal (8:00 AM and 8:00 PM, group B) dosing schedules for 4 weeks each, separated by a 2-week washout period. The budesonide was inhaled through a pressurized metered-dose inhaler, mounted on a 750 ml Nebuhaler (ASTRA Pharmaceuticals, Lund, Sweden). The IgG subclass levels were determined at baseline and every 2 weeks until the end of the study period (10 weeks).

RESULTS

There were no statistically significant changes in the serum IgG subclass concentrations over the 10-week study period in group A, group B, or groups A and B combined.

CONCLUSION

Inhalation of budesonide, 2.4 mg/day, through a large-volume spacer for repeated 1-month periods does not influence serum IgG subclass concentrations in healthy adults, suggesting that budesonide does not cause systemic humoral immunosuppression when given at therapeutic doses.

Age related IgG subclass concentrations in asthma

The prevalence of IgG subclass deficiency in asthma is still controversial. Earlier studies often included patients receiving treatment with systemic steroids which can induce hypogammaglobulinaemia. Concentrations of IgG subclasses were studies in 200 children (aged 2-17 years) with asthma (mean asthma severity score (ASS) 2, range 1-4) who had not received systemic steroids for at least six weeks before investigation, and in 226 healthy age matched controls. The mean concentrations of IgG subclasses in children with asthma were within the 1SD range of those of the control group. In the group with asthma there was a trend towards higher levels of IgG1 and IgG4, whereas the number of children with low concentrations of IgG2 (< 2 SD of control serum samples; absolute concentrations 0.08-1.25 g/l) was slightly greater than in the group who did not have asthma (4.5 v 2.2%). Patients with subnormal concentrations of IgG2 could not be distinguished clinically or on the basis of case history and additional immunological studies did not show further abnormalities. Patients with severe asthma (ASS 3-4) had significantly higher concentrations of IgG4 (mean (SE) 0.53 (0.09) v 0.26 (0.04) g/l) than patients with mild asthma (ASS 1). No significant difference in subclass concentration was found between patients with atopic and those with non-atopic asthma. It is concluded that in an unselected group of children with asthma the mean IgG subclass concentrations do not differ significantly from a group of healthy age matched controls.