The effects of anti-idiotypic antibody on antibody production and apoptosis of anti-dsDNA antibody producing cells

OBJECTIVE

Systemic lupus erythematosus is an autoimmune disease characterized by the production of anti-dsDNA antibody. Because the titer of anti-dsDNA antibody is correlated with disease severity, especially in lupus nephritis, controlling anti-dsDNA antibody production is important in the treatment of SLE. There are many regulatory mechanisms of autoantibody production; one of these is the interaction between idiotype and anti-idiotype antibody (anti-Id). The purpose of the present study was to assess the effect of anti-Id on anti-dsDNA antibody production and apoptosis and to study the mechanism of anti-Id induced apoptosis.

METHODS

After anti-dsDNA antibody producing hybridomas were treated with anti-Id, we checked the amount of anti-dsDNA antibody production, the rate of transcription, cellular proliferation, and apoptosis. Also, after treatment with anti-oxidant (N-acetyl-Lcysteine), phorbol esters with calcium ionophore and corticosteroids, we compared their effect on apoptosis with anti-Id.

RESULTS

Two types of anti-dsDNA antibody producing hybridomas (G1-2, gamma and kappa chains; M2-10, mu and kappa chains) were treated with anti-Id and it was found that: (1) the amount of anti-dsDNA antibody production decreased; (2) the rate of transcription and cellular proliferation did not decrease; and (3) the level of apoptosis increased. The two cells expressed Fas and Fas-ligand, and the Fas of G1-2 was functional but that of M2-10 was not. The treatment of these cells with anti-Id resulted in no change in Fas-ligand and Bax expression, but the expression of Bcl-2 was decreased. In addition, treatment with antioxidant (N-acetyl-L-cysteine) inhibited anti-Id-induced apoptosis in G1-2 and M2-10. Phorbol esters with calcium ionophore also inhibited anti-Id induced apoptosis in M2-10. Corticosteroids induced apoptosis in both cells and showed similar results with anti-Id induced apoptosis.

CONCLUSION

The anti-Id suppressed the production of anti-dsDNA antibody in two cells by inducing apoptosis, as did prednisolone. Furthermore, Bcl-2, oxygen-free radicals and protein kinase C might be involved in the induction of apoptosis by anti-Id.

Evaluation of stress patterns generated by reduction forceps within a photoelastic mandibular model

INTRODUCTION

Little attention has been paid to the mechanical effects of fracture reduction forceps.

AIM

This study aims to evaluate the stress patterns within the fractured mandible generated by reduction forceps.

MATERIAL AND METHODS

Thirty-six mandibular models were fabricated using a photoelastic resin. Each of the three sets of mandibular models was osteotomized according to one of three different fracture types. After reducing the cut segments, reduction forceps were placed into different engagement holes to compress the segments. Photoelastic stress analysis was used to visualize the stress patterns within the fractured mandibular models as generated by the reduction forceps.

RESULTS

In the case of symphyseal or parasymphyseal fractures, an optimum distribution of stresses over the fracture site was achieved when placing the reduction forceps more than 12mm away from either side of the fracture line, between the midway level of the mandibular height (bisecting the mandible) and 5mm below this level. In the case of body fractures, optimum stress distribution was achieved when the reduction forceps were placed more than 16mm from the fracture line at the midway level.

CONCLUSION

Correct use of the reduction forceps helps to provide a precise three-dimensional reduction for mandibular fractures.

An effective technique for open reduction of mandibular angle fractures using new reduction forceps: technical innovations

We demonstrate a new technique that is useful for precompressing and holding mandibular angle fractures by means of new reduction forceps. The forceps were designed for application in the mandibular angle area via a transoral approach.

Chronic hepatitis: in vivo proton MR spectroscopic evaluation of the liver and correlation with histopathologic findings

PURPOSE

To correlate the in vivo hydrogen 1 ((1)H) magnetic resonance (MR) spectroscopic features of the chronic hepatitis-involved liver with the histopathologic stages of fibrosis.

MATERIALS AND METHODS

Seventy-five patients with chronic hepatitis were examined with (1)H MR spectroscopy, which was performed in the right hepatic lobe. The peak areas of glutamine and glutamate complex (Glx), phosphomonoesters (PME), glycogen and glucose complex (Glyu), and lipid were measured on the liver spectra. The histopathologic features were correlated with the in vivo (1)H MR spectroscopic findings at each stage of chronic hepatitis. Fifteen healthy volunteers also were included as a control group.

RESULTS

(1)H MR spectroscopy depicted Glx, PME, Glyu, and lipid in all livers. In the normal livers, the calculated mean (+/- SD) relative metabolite-to-lipid ratios of Glx, PME, and Glyu were 0.14 +/- 0.04, 0.03 +/- 0.01, and 0.21 +/- 0.04, respectively. The mean value of each metabolite-to-lipid ratio was significantly different between all stages of chronic hepatitis, and with the exception of the mean ratio at the interval between stages 0 and 1 (P > .05), the mean value increased significantly with increasing stage (P < .05). A pronounced peak was demonstrated at 3.9-4.1 ppm at (1)H MR spectroscopy of all stages of chronic hepatitis except stage 0.

CONCLUSION

The increased Glx, PME, and Glyu levels relative to the lipid content with chronic hepatitis indicated the severity of fibrosis and thus were concordant with the histopathologic stages. In vivo (1)H MR spectroscopy might be a substitute for liver biopsy in the diagnosis and staging of chronic hepatitis.

Oligoclonal B lymphocyte expansion in the synovium of a patient with Behçet's disease

OBJECTIVE

Plasma cell infiltration is observed in recurrent arthritis associated with Behçet's disease (BD). The immune mechanism underlying B lymphocyte proliferation in the synovium is unclear. One hypothesis involves nonspecific polyclonal activation and another involves antigen-driven activation. The present study was undertaken to test both hypotheses and identify immunoglobulin genes that are clonally expanded in the synovium.

METHODS

Peripheral blood lymphocytes (PBL) and synovial cells from a patient with BD and PBL from a healthy control subject were obtained. Complementarity-determining region 3 (CDR3) fingerprinting analysis and nucleotide sequence analysis of Ig transcripts derived from clonally expanded B lymphocytes were performed in parallel.

RESULTS

Of 44 mu heavy chain clones of the VH4 family identified in the synovial tissue from the BD patient, 8 clones showed identical nucleotide sequences, and therefore, 18.2% were clonally expanded. For y heavy chain, 4 of 50 clones of the VH3 family showed nearly identical sequences; therefore, 4-8% were clonally expanded. The kappa light chain did not show a dominant band, but a clone with a 12-amino acid CDR3 showed 3% clonal expansion. Somatic mutations were frequently observed, with a high ratio of replacement to silent mutations in the CDRs compared with the framework regions. Three Ig genes expressed in the clonally expanded B lymphocytes were derived from germline gene segments reported to be involved in the production of autoantibodies.

CONCLUSION

These results support the hypothesis that antigen-driven clonal B lymphocyte proliferation occurs in the synovium in BD. Immunoglobulin transcripts clonally expanded in the synovium were identified.

Risk factors for infection and role of C-reactive protein in Korean patients with systemic lupus erythematosus

To evaluate risk factors for infection and the role of C-reactive protein (CRP) in the diagnosis of infection, a retrospective case control study was performed among Korean systemic lupus erythematosus patients. Of 120 proven infections, 31 episodes (25.8%) occurred in patients taking no corticosteroids (CS). The risk of infection was lower in patients taking low-dose CS (< 300 mg prednisolone/month) than no CS (odds ratio (OR) 0.36). In patients receiving high-dose CS (> 1000 mg prednisolone/month), however, the risk increased (OR 2.9). In patients taking no CS, disease activity manifested as increased SLEDAI, anemia and active urinary sediment, was associated with infection. The CRP was higher in the patients with infection than controls and the CRP levels over 50 mg/l were observed only in infection. These results suggest that CS have a bimodal influence on infection depending on dose. Disease activity is an important risk factor for infection in patients taking no CS. Finally, CRP levels greater than 50 mg/l suggest the presence of infection.

Proliferating trichilemmal tumors: CT and MR imaging findings in two cases, one with malignant transformation

We report the imaging findings in two patients with proliferating trichilemmal tumors. In the first patient, the tumor arose on the lower lip, a very unusual location for this type of tumor, and showed malignant transformation with metastasis to a regional lymph node. It was seen as a poorly marginated soft-tissue mass with isointense signal on T1-weighted MR images and hyperintense signal on T2-weighted images. Large areas of high signal intensity caused by necrosis were also found within the tumor on T2-weighted images. After i.v. administration of contrast material, the mass showed significant enhancement, with considerable portions remaining unenhanced. In the second patient, the tumor originated from a preexisting trichilemmal cyst and occurred in the hair-bearing area of the posterior part of the neck. CT scans showed a well-encapsulated cystic mass that contained multiple speckled calcifications in a wall of variable thickness. There were several foci of smooth soft-tissue elevations from the inner wall of the mass, which corresponded histologically to proliferating portions of trichilemmal cyst.

Aggressive epithelial odontogenic ghost cell tumor in the mandible: CT and MR imaging findings

We report a case of aggressive epithelial odontogenic ghost cell tumor arising from the mandible in a 32-year-old man. On CT and MR studies, the tumor was seen as a large, heterogeneous soft-tissue mass that caused marked destruction of the mandible and invaded the mouth floor and tongue base. The tumor displayed a variety of densities and signal intensities on CT and MR images, which correlated well with the degree of cellularity of epithelial islands, abundance of ghost cells and eosinophilic materials, calcification, and cystic areas on histologic sections. Owing to the unpredictable biological behavior of this type of tumor, careful, long-term follow-up is highly recommended.

Helical CT angiography and three-dimensional reconstruction of total anomalous pulmonary venous connections in neonates and infants

OBJECTIVE

The objective of this study was to investigate the usefulness of helical CT angiography in the evaluation of total anomalous pulmonary venous connections.

MATERIALS AND METHODS

Fourteen patients with total anomalous pulmonary venous connections underwent helical CT angiography and subsequent three-dimensional (3D) reconstruction. They ranged in age from 3 days to 8 months (median age, 2.3 months) and in weight from 2.3 to 7.1 kg (median weight, 4.3 kg). The types of total anomalous pulmonary venous connections and the number of pulmonary veins were evaluated on axial and 3D images. Qualitative evaluations were performed for extent of pulmonary vascular enhancement and contrast- or motion-induced artifacts.

RESULTS

In all patients, helical CT angiography correctly depicted total anomalous pulmonary venous connections. Seven cases were the supracardiac type, four cases were the cardiac type, one case was the infracardiac type, and two cases were the mixed type. The detection rate of the pulmonary vein in 3D reconstruction images (95-98%) was slightly lower than that of the pulmonary vein in the axial images (100%), but the difference between axial and 3D reconstruction images was not statistically significant (p > 0.1). No statistically significant differences were noted among 3D reconstruction images in the detection rates of the pulmonary vein (p > 0.1). The extent of contrast enhancement of the pulmonary vein was good or excellent in all patients. In five patients, there were contrast-induced artifacts that made some surrounding vascular distortion but did not interfere with the pulmonary vein analysis, except in one patient. Motion-induced artifacts were observed in nine patients. One of them had an obstacle in pulmonary vein analysis.

CONCLUSION

The combination of axial and 3D images in helical CT angiography is helpful in the assessment of a total anomalous pulmonary venous connection containing the individual pulmonary vein, and this combination can be a good diagnostic tool in preoperative evaluation of neonates and infants with a total anomalous pulmonary venous connection.

Systemic lupus erythematosus: brain MR imaging and single-voxel hydrogen 1 MR spectroscopy

PURPOSE

To evaluate the usefulness of magnetic resonance (MR) imaging and hydrogen 1 MR spectroscopy in the detection of brain involvement in patients with systemic lupus erythematosus (SLE) with or without neuropsychiatric symptoms.

MATERIALS AND METHODS

Twenty-six patients who had SLE with (n = 17) or without (n = 9) neuropsychiatric symptoms were examined at MR imaging and (1)H MR spectroscopy. The voxel was placed in the basal ganglia and peritrigonal white matter. Eight healthy volunteers were included.

RESULTS

Five of nine patients with major neuropsychiatric symptoms and one of eight patients with minor neuropsychiatric symptoms had abnormal MR imaging findings. (1)H MR spectroscopy showed a significantly decreased N:-acetylaspartate-creatine (Cr) ratio in the basal ganglia and an increased choline-Cr ratio in the peritrigonal white matter in patients with major symptoms compared with those with minor symptoms, those without symptoms, and healthy control subjects. Among patients with major symptoms, there was no difference in metabolite ratios between those with and those without abnormal MR imaging findings. Among patients with normal MR imaging findings, abnormal spectral changes were observed only in those with major neuropsychiatric symptoms. In patients without neuropsychiatric symptoms, results of (1)H MR spectroscopy and MR imaging were normal.

CONCLUSION

In patients with SLE, (1)H MR spectroscopic findings seem to reflect the cerebral metabolic disturbance related to the severity of the neuropsychiatric symptoms and are not related to the presence of abnormal MR imaging findings.

Malignant fibrous histiocytoma: an ultrastructural perspective

Malignant fibrous histiocytoma is a frequent diagnosis, but the relationship of the tumors to histologically similar soft tissue neoplasms is controversial. In this study, 157 examples representing the 4 main subtypes were reviewed by light microscopy and each tumor was studied with the electron microscope. Immunohistochemical stains were performed on 77 tumors. Electron micrographs on 100 fibrosarcomas were reviewed for comparison. Malignant fibrous histiocytomas often closely resemble fibrosarcomas at the ultrastructural level and differences between the two are generally of degree only. Evidence for true histiocytic differentiation was not found. The immunohistochemical results did not contradict the authors' impression from electron microscopy that malignant fibrous histiocytoma forms part of the histologic spectrum of tumors of fibroblasts.

Clinical manifestations of Korean female gouty patients

In an endeavor to analyse the clinical characteristics of female gout, we reviewed 36 women with gout. Twenty-seven (75%) developed the first symptomatic episode of gout after the onset of the menopause. The mean age at onset of gout was 54.3 years (range 15-87 years). Twenty-two patients (61%) had hypertension, 17 (47%) had renal insufficiency, 13 (36%) used diuretics and 10 (28%) were taking cyclosporine for a renal allograft. Tophaceous gout occurred in 10 patients (27%) and polyarticular involvement was seen in 16 (44%) at initial presentation. Five of nine premenopausal patients were taking cyclosporine and four had renal insufficiency. A comparison with a control group of 72 randomly selected male patients with gout showed that the female patients were frequently receiving diuretics at the time of the attack and had significantly lower mean uric acid excretion, whereas significantly more male patients showed heavy alcohol consumption and precipitating events for an acute attack compared with the female patients. There were no significant differences between the sexes for onset age, hypertension, renal insufficiency, distribution of joint involvement, tophi and mean serum uric acid concentration. The female patients in this study had a lower mean age at onset of gout than in previous studies, which was attributed to the inclusion of renal transplantation patients. Transplantation gout patients receiving cyclosporine lower the mean age at onset of female gout and this is an emerging problem in female gout.

Pilomatricoma in the head and neck: CT findings in three patients

We report three cases of pilomatricoma, one in the infrahyoid neck and the others in the preauricular area. In all cases, CT showed well marginated soft tissue masses that were located mainly in the subcutaneous fat, partly attaching to the overlying skin. There was no evidence of infiltration to deeper structures. Substantial amounts of calcification were found in one tumor. Pilomatricoma should be included in diagnostic consideration when CT shows a well marginated subcutaneous soft tissue mass adherent to the skin with or without visible calcification in the head and neck region.

Lipid profiles in untreated patients with rheumatoid arthritis

OBJECTIVE

To investigate lipid profiles in patients with untreated active rheumatoid arthritis (RA) and to assess the relationship of the inflammatory condition of RA with lipid profiles.

METHODS

Forty-two patients with RA and 42 age and sex matched healthy controls were studied. Patients with RA had not been treated with corticosteroid or disease modifying antirheumatic drugs prior to the study. Total cholesterol, triglyceride, HDL-cholesterol, LDL-cholesterol, apolipoprotein A1 (apo A1), apolipoprotein B (apo B), lipoprotein(a) [Lp(a)], and C-reactive protein (CRP) were measured in both groups.

RESULTS

The levels of apo A1 and HDL-cholesterol were significantly lower in patients than in controls (128.5 vs. 151.8 mg/dl, 41.2 vs. 54.9 mg/dl, respectively). The level of Lp(a) was significantly higher in patients than in controls (27.1 vs. 18.0 mg/dl). The ratios of apo B/apo A1, total cholesterol/HDL-cholesterol, and LDL-cholesterol/HDL-cholesterol were significantly higher in patients than in controls (0.82 vs. 0.67, 4.4 vs. 3.4, 2.8 vs. 1.9, respectively). CRP showed a significant correlation with apo A1 (r = -0.44, p<0.01) and HDL-cholesterol (r = -0.35, p<0.05).

CONCLUSION

Our study suggests that patients with untreated active RA have altered lipoprotein and apolipoprotein patterns that may possibly expose them to higher risk of atherosclerosis. The inflammatory condition of RA may affect the metabolism of HDL-cholesterol and apo A1.

Elevated serum interleukin-15 levels in systemic lupus erythematosus

Interleukin-15 (IL-15) has multiple biological properties, including the induction of other cytokine production and the inhibition of T cell apoptosis. Recently, IL-15 was reported to have a major role in synovial inflammation of rheumatoid arthritis, and that it provokes and amplifies the inflammatory process through the activation of TNF-alpha production. In systemic lupus erythematosus (SLE), the dysregulation of apoptosis and various cytokine production were observed and have been implicated in the pathogenesis of SLE. Thus, we tried to determine serum IL-15 levels in SLE patients and to assess the relationship among IL-15 levels, TNF-alpha levels and disease activity of SLE. Twenty SLE patients and 10 controls were studied. Paired serum samples were collected from all SLE patients at the time of presentation with active disease and at 4 weeks after institution of treatment. IL-15 levels were determined by ELISA and compared with the disease activity indices in SLE. The disease activity of SLE was measured using the SLE Disease Activity Index (SLEDAI) and laboratory parameters such as circulating immune complex (CIC), C3, C4, anti-DNA antibody, IgG, IgM, and IgA. The IL-15 levels in SLE patients were significantly higher than those of controls (5.38 +/- 4.89 vs. 1.04 +/- 1.26 pg/ml). However, elevated IL-15 levels did not correlate with the SLEDAI, nor did they correlate with other laboratory activity indices. The changes in serum IL-15 levels did not correlate with the changes in serum TNF-alpha in the disease course of SLE patients, whereas TNF-alpha reflected the changes in disease activity of SLE. Serum levels of IL-15 are elevated in SLE patients, but IL-15 did not correlate with the disease activity of SLE. TNF-alpha production in SLE patients was unlikely to be related with IL-15.

Presence of specific IgG antibody to grain dust does not go with respiratory symptoms

A high prevalence of work-related symptoms in relation to grain dust exposure has been reported in grain dust workers, but the role of the specific IgG antibody is unknown. To study the possible role of specific IgG (sIgG) and specific IgG4 (sIgG4) in the development of work-related symptoms, sIgG and sIgG4 subclass antibodies against grain dust antigens were determined by ELISA in sera from 43 workers and 27 non-exposed controls. They were compared with results of specific IgE antibodies, exposure intensity and the presence of respiratory symptoms. SIgG and sIgG4 antibodies were detectable in almost all sera of exposed workers, and the prevalence were significantly higher than those of controls (p<0.05). Higher sIgG4 was noted in workers with specific IgE (p<0.05). The correlation between sIgG and exposure duration was significant (p<0.05). There was no association between the prevalence of sIgG and sIgG4 and the presence of respiratory symptoms, or work stations. In conclusion, these results suggest that the existence of sIgG and sIgG4 might represent a response to grain dust exposure and may unlikely play a role in the etiology of respiratory symptoms.

Ileal obstruction caused by idiopathic sclerosing encapsulating peritonitis

A 26-year-old woman presented with epigastric pain, vomiting, and a palpable mass in the right lower abdomen. Ultrasonography showed a high echogenic mass associated with a small amount of ascites in the right lower abdomen. Computed tomography demonstrated entrapped ileal loops within a thin-walled fibrous capsule. A thin fibrous sac encasing the terminal ileum was detected on laparotomy and confirmed as idiopathic sclerosing encapsulating peritonitis.

A case of small cell carcinoma arising in a mature cystic teratoma of the ovary

Malignant transformation of ovarian mature cystic teratomas is reported to occur in about 1% of cases. The most common malignant evolution is that of squamous cell carcinoma and one of the least common is that of small cell carcinoma. We report a case of distant metastasis from a small cell carcinoma arising in a mature cystic teratoma. A 28-year-old nulliparous female presented with signs of supraclavicular lymph node metastasis. This is the first known case report of lymph node metastasis as an initial sign of cancer developing in a pre-existing mature cystic teratoma. Histologically, the tumor cells had microscopic features similar to those of pulmonary small cell carcinoma. This report gives a literature review, and the histological, immunohistochemical, flow cytometric and ultrastructural features are described.

Giant hidradenocarcinoma: a report of malignant transformation from nodular hidradenoma

A giant hidradenocarcinoma presented by a 75-year-old female is reported. The patient had a malignant transformation within a nodular hidradenoma involving the right postauricular area, which was treated by mass removal and a right radical neck dissection with a free-flap covering. Malignant hidradenocarcinoma is the least common adnexal tumor of uncertain origin. They are usually malignant from their inception, but some develop from a benign counterpart. To the authors' knowledge, only three cases have been reported previously. Two histologically distinct components were seen in this tumor: (i) typical nodular hidradenoma, which constituted a small part of the tumor; and (ii) carcinoma with areas of transition. The secretory cells of hidradenocarcinoma showed decapitation secretion on light and electron microscopic observations, which is evidence of apocrine differentiation. Histologically, this case was concluded as a hidradenocarcinoma arising from a long-standing nodular hidradenoma. A literature review is presented and the histological, immunohistochemical and ultrastructural features are described.

Oilseed rape allergy presented as occupational asthma in the grain industry

BACKGROUND

There have been several reports on respiratory allergic symptoms induced by pollen of oilseed rape. To the best of our knowledge, this is the first report dealing with oilseed rape dust mainly composed of seeds, as an occupational allergen in the grain industry. In this paper, we present a case of occupational asthma caused by oilseed rape dust from the Animal Feed Industry, which proved to be induced by an IgE-mediated reaction.

METHODS AND RESULTS

The patient displayed positive responses to Dermatophagoides farinae as well as oilseed rape dust extract. The bronchoprovocation test showed an early asthmatic response to oilseed rape dust extract. Serum specific IgE antibody to oilseed rape antigen was detected by enzyme-linked immunosorbent assay (ELISA). ELISA inhibition test showed significant inhibitions with addition of oilseed rape antigen. In order to further identify the allergenic components of extract, sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblot analysis were performed. Fourteen IgE-binding components ranging from 10 to 160kDa were detected within the oilseed rape extract.

CONCLUSION

These results suggest that the inhalation of oilseed rape dust, not pollen, can cause IgE mediated bronchoconstriction in an exposed worker of the grain industry.

Role of specific IgE, IgG and IgG4 antibodies to corn dust in exposed workers

BACKGROUND AND METHODS

To evaluate the role of specific antibodies to corn dust (CD) and their relationship to respiratory dysfunction, we detected serum specific IgE(slgE) and IgG4(slgG4) antibodies by ELISA in 42 employees working in the animal feed industry and 27 unexposed controls.

RESULTS

Our survey revealed that 15 (34.9%) subjects had work-related respiratory dysfunction associated with or without nasal symptoms. Among these subjects, eight had airway hyper-responsiveness to methacholine. Significant differences were noted in slgE and slgG4 between exposed and unexposed groups (p = 0.04, p = 0.00 respectively), but no difference was noted in slgG (p = 0.1). Although there was no significant differences in the prevalence of specific IgE antibody between symptomatic (29%) and asymptomatic groups (19%, p = 0.55), the specific IgE levels were significantly higher in symptomatic workers than in asymptomatic workers (p = 0.03). Specific IgG antibody was detected in 1 (6%) symptomatic and 4 (15%) asymptomatic workers (p = 0.46). Specific IgG4 antibody was detected in 11 (73%) of symptomatic and 21 (78%) of asymptomatic workers (p = 0.90). The higher prevalence of slgG4 antibody was noted in workers with slgE antibody (p = 0.001). The correlation between slgG and exposure duration was significant (r = 0.36, p = 0.02). There was no association between the prevalence of slgE, slgG, and slgG4 to exposure intensity, smoking or atopic status.

CONCLUSION

These results suggested that the existence of slgG and slgG4 might represent a response to CD exposure, and that some unexposed subjects had slgG to CD. Specific IgE might play a role in the development of respiratory symptoms.