Localisation of a pulmonary autoantigen in cryptogenic fibrosing alveolitis

Intrapulmonary Autoantibodies to HSP72 Are Associated with Improved Outcomes in IPF

Rationale

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic interstitial lung disease, with high mortality. Currently, the aetiology and the pathology of IPF are poorly understood, with both innate and adaptive responses previously being implicated in the disease pathogenesis. Heat shock proteins (Hsp) and antibodies to Hsp in patients with IPF have been suggested as therapeutic targets and prognostic biomarkers, respectively. We aimed to study the relationship between the expression of Hsp72 and anti-Hsp72 antibodies in the BAL fluid and serum Aw disease progression in patients with IPF.

Methods

A novel indirect ELISA to measure anti-Hsp72 IgG was developed and together with commercially available ELISAs used to detect Hsp72 IgG, Hsp72 IgGAM, and Hsp72 antigen, in the serum and BALf of a cohort of IPF (n = 107) and other interstitial lung disease (ILD) patients (n = 66). Immunohistochemistry was used to detect Hsp72 in lung tissue. The cytokine expression from monocyte-derived macrophages was measured by ELISA.

Results

Anti-Hsp72 IgG was detectable in the serum and BALf of IPF (n = 107) and other ILDs (n = 66). Total immunoglobulin concentrations in the BALf showed an excessive adaptive response in IPF compared to other ILDs and healthy controls (p = 0.026). Immunohistochemistry detection of C4d and Hsp72 showed that these antibodies may be targeting high expressing Hsp72 type II alveolar epithelial cells. However, detection of anti-Hsp72 antibodies in the BALf revealed that increasing concentrations were associated with improved patient survival (adjusted HR 0.62, 95% CI 0.45-0.85; p = 0.003). In vitro experiments demonstrate that anti-Hsp72 complexes stimulate macrophages to secrete CXCL8 and CCL18.

Conclusion

Our results indicate that intrapulmonary anti-Hsp72 antibodies are associated with improved outcomes in IPF. These may represent natural autoantibodies, and anti-Hsp72 IgM and IgA may provide a beneficial role in disease pathogenesis, though the mechanism of action for this has yet to be determined.

Anti-parietal cell autoimmunity is associated with an accelerated decline of lung function in IPF patients

BACKGROUND

Autoantibodies against lung epithelial antigens are often detected in patients with Idiopathic Pulmonary Fibrosis (IPF). Anti-Parietal Cell Antibodies (APCA) target the H+/K+ATPase (proton pump). APCA prevalence and lung H+/K+ATPase expression was never studied in IPF patients.

METHODS

We retrospectively collected clinical, lung function and imaging data from APCA positive patients (APCA+IPF) and compared them with APCA negative IPF patients matched on the date of diagnostic assessment. H+/K+ATPase expression was assessed with immunohistochemistry and PCR.

RESULTS

Among 138 IPF patients diagnosed between 2007 and 2014 and tested for APCA, 19 (13.7%) APCA+ patients were identified. APCA+IPF patients were 16 men and 3 women, mean age 71 years. The median titer of APCA was 1:160. A pernicious anemia was present in 5 patients and preceded the fibrosis in 3 cases. With a mean follow up of 31 months, 2 patients had an exacerbation and 7 patients died. As compared with 19 APCA- IPF patients, APCA+IPF patients had a less severe disease with better DLCO (57% vs 43% predicted), preserved PaO₂ (85 ± 8 mmHg vs 74 ± 11 mmHg), a lower rate of honeycombing on HRCT (58% vs 89%), but they experienced an accelerated decline of FVC (difference 61.4 ml/year; p = .0002). The H+/K+ATPase was strongly expressed by hyperplastic alveolar epithelial cells in the fibrotic lung.

CONCLUSION

Anti-parietal cell autoimmunity is detected in some IPF patients and is associated with an accelerated decline of lung function. Anti-parietal cell autoimmunity may promote lung fibrosis progression.

The pathogenesis of bleomycin-induced lung injury in animals and its applicability to human idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a devastating disease of unknown etiology, for which there is no curative pharmacological therapy. Bleomycin, an anti-neoplastic agent that causes lung fibrosis in human patients has been used extensively in rodent models to mimic IPF. In this review, we compare the pathogenesis and histological features of human IPF and bleomycin-induced pulmonary fibrosis (BPF) induced in rodents by intratracheal delivery. We discuss the current understanding of IPF and BPF disease development, from the contribution of alveolar epithelial cells and inflammation to the role of fibroblasts and cytokines, and draw conclusions about what we have learned from the intratracheal bleomycin model of lung fibrosis.

New treatment and markers of prognosis for idiopathic pulmonary fibrosis: lessons learned from translational research

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive interstitial lung disease with increasing prevalence, high mortality rates and poor treatment options. The diagnostic process is complex and often requires an interdisciplinary approach between different specialists. Information gained over the past 10 years of intense research resulted in improved diagnostic algorithms, a better understanding of the underlying pathogenesis and the development of new therapeutic options. Specifically, the change from the traditional concept that viewed IPF as a chronic inflammatory disorder to the current belief that is primarily resulting from aberrant wound healing enabled the identification of novel treatment targets. This increased the clinical trial activity dramatically and resulted in the approval of the first IPF-specific therapy in many countries. Still, the natural history and intrinsic behavior of IPF are very difficult to predict. There is an urgent need for new therapies and also for development and validation of prognostic markers that predict disease progression, survival and also response to antifibrotic drugs. This review provides an up to date summary of the most relevant clinical trials, novel therapeutic drug targets and outlines a spectrum of potential prognostic biomarkers for IPF.

Molecular and cellular mechanisms of pulmonary fibrosis

Pulmonary fibrosis is a chronic lung disease characterized by excessive accumulation of extracellular matrix (ECM) and remodeling of the lung architecture. Idiopathic pulmonary fibrosis is considered the most common and severe form of the disease, with a median survival of approximately three years and no proven effective therapy. Despite the fact that effective treatments are absent and the precise mechanisms that drive fibrosis in most patients remain incompletely understood, an extensive body of scientific literature regarding pulmonary fibrosis has accumulated over the past 35 years. In this review, we discuss three broad areas which have been explored that may be responsible for the combination of altered lung fibroblasts, loss of alveolar epithelial cells, and excessive accumulation of ECM: inflammation and immune mechanisms, oxidative stress and oxidative signaling, and procoagulant mechanisms. We discuss each of these processes separately to facilitate clarity, but certainly significant interplay will occur amongst these pathways in patients with this disease.

Idiopathic pulmonary fibrosis is associated with circulating antiepithelial antibodies

PURPOSE

Idiopathic pulmonary fibrosis (IPF) is a restrictive fibrotic lung disease of uncertain etiology. Alveolar epithelial injury may be one of the inciting triggers in the pathogenesis of this disorder. We hypothesized that circulating antibodies to alveolar epithelial and endothelial cells may be involved in the pathogenesis of IPF.

METHODS

Antibodies to alveolar epithelial and endothelial cells were analyzed by indirect immunofluorescence using alveolar epithelial cells (A549) and human umbilical vein endothelial cells respectively. IgG and IgM antibodies in patients' serum were evaluated. Patterns of immunofluorescence, including membranous, cytoplasmic, and nuclear staining, were analyzed by fluorescence microscopy. The severity of immunofluorescence was divided into mild, moderate, and severe categories. Fifty-six patients (IPF = 28, non-IPF ILD = 9, non-ILD control = 19) were evaluated for antiepithelial antibodies, and 28 patients (IPF = 12, non-IPF ILD = 3, non-ILD control = 13) were studied for antiendothelial antibodies.

RESULTS

Compared with control subjects, serum from IPF patients displayed significantly higher IgG binding to alveolar epithelial cells (P = 0.041) with a membranous pattern of immunofluorescence. However, there was no significant difference in immunofluorescence with IgG on endothelial cells (P = 0.165). In terms of IgM antibodies, there was no differential fluorescence observed for either epithelial or endothelial cells.

CONCLUSIONS

There is evidence of increased IgG antibodies directed against alveolar epithelium in IPF. These antibodies may play a significant role in the pathogenesis of this fibrotic disorder. The findings of this study suggest further evaluation of the role of immune mediated alveolar epithelial injury in IPF.

Idiopathic pulmonary fibrosis-an epidemiological and pathological review

Idiopathic pulmonary fibrosis (IPF) is an interstitial lung disease (ILD) affecting the pulmonary interstitium. Other forms of interstitial lung disease exist, and in some cases, an environmental etiology can be delineated. The diagnosis of IPF is typically established by high-resolution CT scan. IPF tends to have a worse prognosis than other forms of ILD. Familial cases of IPF also exist, suggesting a genetic predisposition; telomerase mutations have been observed to occur in familial IPF, which may also explain the increase in IPF with advancing age. Alveolar epithelial cells are believed to be the primary target of environmental agents that have been putatively associated with IPF. These agents may include toxins, viruses, or the autoantibodies found in collagen vascular diseases. The mechanism of disease is still unclear in IPF, but aberrations in fibroblast differentiation, activation, and proliferation may play a role. Epithelial-mesenchymal transition may also be an important factor in the pathogenesis, as it may lead to accumulation of fibroblasts in the lung and a disruption of normal tissue structure. Abnormalities in other components of the immune system, including T cells, B cells, and dendritic cells, as well as the development of ectopic lymphoid tissue, have also been observed to occur in IPF and may play a role in the stimulation of fibrosis that is a hallmark of the disease. It is becoming increasingly clear that the pathogenesis of IPF is indeed a complex and convoluted process that involves numerous cell types and humoral factors.

Oxidative damage and TGF-β differentially induce lung epithelial cell sonic hedgehog and tenascin-C expression: implications for the regulation of lung remodelling in idiopathic interstitial lung disease

Idiopathic interstitial lung diseases (iILDs) are characterized by inflammation, hyperplasia of Type-II alveolar epithelial cells (AECs) and lung remodelling often with progressive fibrosis. It remains unclear which signals initiate iILD and/or maintain the disease processes. Using real-time RT-PCR and immunohistochemistry on archival biopsies of three patterns of iILD (usual interstitial pneumonitis/UIP, non-specific interstitial pneumonitis/NSIP and cryptogenic organizing pneumonia/COP) we investigated whether hedgehog signalling (previously associated with lung damage and repair) was functional and whether the damage associated extracellular matrix protein tenascin-C was present in activated Type-II AECs in all three iILDs. Using tissue culture, protein and mRNA detection we also determined how two signals (oxidative damage and TGF-β) associated with iILD pathogenesis affected Sonic hedgehog (SHH) and tenascin-C production by a Type-II AEC cell line. We report that SHH pathway and tenascin-C mRNA and proteins were found in UIP, NSIP and COP. SHH signalling was most active at sites of immature organizing fibrous tissue (fibroblastic foci) in UIP. In vitro Type-II AECs constitutively secrete SHH but not tenascin-C. Oxidative injury stimulated SHH release whereas TGF-β inhibited it. TGF-β and oxidative damage both upregulated tenascin-C mRNA but only TGF-β induced synthesis and release of a distinct protein isoform. SHH signalling is active in Type-II AECs from three types of ILD and all three express tenascin-C.

Identification of periplakin as a new target for autoreactivity in idiopathic pulmonary fibrosis

RATIONALE

Injury to alveolar epithelial cells is central to the pathophysiology of idiopathic pulmonary fibrosis (IPF). An abnormal autoimmune response directed against antigens of the alveolar epithelium may contribute to the disease.

OBJECTIVES

To detect circulating autoantibodies (autoAbs) directed against epithelial structures.

METHODS

We performed immunoblot by separating human placental amnion extract or alveolar epithelial cell (A549 cell line) proteins on polyacrylamide gels, blotting on nitrocellulose membranes, and incubating with serum from patients with IPF (n = 40) or healthy subjects (n = 40). Proteomic analysis and mass spectrometry characterized the target protein. Inhibition experiments performed with the correspondent recombinant protein confirmed our results.

MEASUREMENTS AND MAIN RESULTS

We identified IgG autoAbs recognizing a 200-kD protein in the serum of patients with IPF. Proteomic analysis identified this protein as human periplakin (PPL), a component of desmosomes. Anti-PPL Abs were found by immunoblot in both serum and bronchoalveolar lavage in patients with IPF: 16/40 (40%) of them were positive versus none of the control subjects. Immunohistochemistry revealed that PPL was strongly expressed in bronchial and alveolar epithelium, but that PPL exhibited changes in intracellular localization among normal and fibrotic alveolar epithelium. In an alveolar epithelial wound repair assay, an anti-PPL IgG decreased cell migration. Recombinant PPL induced bronchoalveolar lavage T lymphocyte proliferation. Patients with IPF with anti-PPL Abs had a more severe respiratory disease, despite no difference in survival.

CONCLUSIONS

We found a new circulating autoAb directed against PPL in patients with IPF, associated with a more severe disease.

CD28 down-regulation on circulating CD4 T-cells is associated with poor prognoses of patients with idiopathic pulmonary fibrosis

Background

Although the etiology of idiopathic pulmonary fibrosis (IPF) remains perplexing, adaptive immune activation is evident among many afflicted patients. Repeated cycles of antigen-induced proliferation cause T-cells to lose surface expression of CD28, and we hypothesized this process might also occur in IPF.

Methodology/Principal Findings

Peripheral blood CD4 T-cells from 89 IPF patients were analyzed by flow cytometry and cytokine multiplex assays, and correlated with clinical events. In comparison to autologous CD4⁺CD28⁺cells, the unusual CD4⁺CD28^null lymphocytes seen in many IPF patients had discordant expressions of activation markers, more frequently produced cytotoxic mediators perforin (2.4±0.8% vs. 60.0±7.4%, p<0.0001) and granzyme B (4.5±2.8% vs.74.9±6.5%, p<0.0001), produced greater amounts of many pro-inflammatory cytokines, and less frequently expressed the regulatory T-cell marker FoxP3 (12.9±1.1% vs. 3.3±0.6% p<0.0001). Infiltration of CD4⁺CD28^null T-cells in IPF lungs was confirmed by confocal microscopy. Interval changes of CD28 expression among subjects who had replicate studies were correlated with conterminous changes of their forced vital capacities (r_s = 0.49, p = 0.012). Most importantly, one-year freedom from major adverse clinical events (either death or lung transplantation) was 56±6% among 78 IPF patients with CD4⁺CD28⁺/CD4_total≥82%, compared to 9±9% among those with more extensive CD28 down-regulation (CD4⁺CD28⁺/CD4_total<82%) (p = 0.0004). The odds ratio for major adverse events among those with the most extensive CD28 down-regulation was 13.0, with 95% confidence intervals 1.6-111.1.

Conclusions/Significance

Marked down-regulation of CD28 on circulating CD4 T-cells, a result of repeated antigen-driven proliferations, is associated with poor outcomes in IPF patients. The CD4⁺CD28^null cells of these patients have potentially enhanced pathogenic characteristics, including increased productions of cytotoxic mediators and pro-inflammatory cytokines. These findings show proliferative T-cell responses to antigen(s) resulting in CD28 down-regulation are associated with progression and manifestations of IPF, and suggest assays of circulating CD4 T-cells may identify patients at greatest risk for clinical deterioration.

Identification of annexin 1 as a novel autoantigen in acute exacerbation of idiopathic pulmonary fibrosis

Consistent with the hypothesis that pulmonary epithelial apoptosis is the key to the acute exacerbation of idiopathic pulmonary fibrosis (IPF), we conducted serological identification of Ags by recombinant expression cloning (SEREX) analysis using type II alveolar cell carcinoma (A549) cell lines to identify disease-related Abs. In a survey of Abs to the recombinant autoantigens identified by SEREX analysis, five Abs were identified as novel candidates for the acute exacerbation of IPF. Abs to annexin 1 were detected in 47 and 53% of the sera and bronchoalveolar lavage materials from patients with acute exacerbation of IPF. Some identical TCR Vbeta genes were identified in sequential materials obtained at 1-3 mo in all 10 acute exacerbation IPF cases, suggesting that some infiltrating CD4-positive T cells sharing limited epitopes expand by Ag-driven stimulation during disease extension. The CDR3 region of these identical TCR Vbeta genes showed high homology with the N-terminal portion of annexin 1, including in the HLA-DR ligand epitopes predicted by TEPITOPE analysis. By Western blotting analysis and observation of the CD4-positive T cell responses in bronchoalveolar lavage samples, the N-terminal portion of annexin 1 was cleaved and found to induce marked proliferative responses of CD4-positive T cells in three patients. Our study demonstrates that annexin 1 is an autoantigen that raises both Ab production and T cell response in patients with acute exacerbation of IPF, and that the N-terminal portion of annexin 1 plays some role in the pathogenesis of acute exacerbation in IPF patients.

Autoantibody to alanyl-tRNA synthetase in patients with idiopathic pulmonary fibrosis

BACKGROUND AND OBJECTIVES

The pathogenesis of IPF is unknown and it is hypothesized that immunological responses are involved. The purpose of this study was to detect autoantibodies in IPF patients and to identify the relevant antigens.

METHODS

Sera from 37 healthy subjects and 22 IPF patients who had no clinical symptoms of collagen vascular disease were examined for immunostaining of A549 human type II cells and human lung tissue. Immunoprecipitation and proteome analysis were performed to identify the antigen.

RESULTS

Fifty per cent of the patient sera and none of the control sera exhibited positive staining. Sera from 10 of the 22 IPF patients showed positive immunohistochemistry and immunoprecipitated a 110-kDa protein from the A549 cell lysate. Sera from only two of 41 patients with collagen vascular disease showed positive immunoreactivity. Proteome analysis using tandem mass spectrometry revealed that the protein was alanyl-tRNA synthetase. Transfection of cDNA of this enzyme into CHO-K1 cells conferred positive staining on these cells with the patients' IgG. The 135-kDa fusion protein consisting of 108-kDa enzyme protein and 27-kDa YFP from the cell lysate of the transfected cells was immunoprecipitated by the patient IgG. In addition, sera from IPF patients significantly inhibited the enzyme activity of alanyl-tRNA synthetase.

CONCLUSION

A significant number of IPF patients possess circulating autoantibodies against alanyl-tRNA synthetase, suggesting the involvement of an autoimmune background in the pathogenesis of IPF.

Fibroblast foci are not discrete sites of lung injury or repair: the fibroblast reticulum

BACKGROUND

Usual interstitial pneumonia (UIP), the pathologic correlate of idiopathic pulmonary fibrosis, contains characteristic discrete areas of fibroblasts, myofibroblasts, and newly formed collagen, termed "fibroblast foci." These lesions are argued to represent isolated sites of recurrent acute lung injury and suggested to be the mechanism of disease progression. We hypothesized that, rather than isolated, these lesions are part of an organized neoplasm.

METHODS

Morphometric analysis of pentachrome-stained histologic sections of UIP was performed. Using point-counting technique on serial sections, fibroblast foci, arteries, and macrophage clusters were identified and we determined their individual "connectiveness" by estimating the Euler number. Two-dimensional micrographs were collated into a three-dimensional array from which a visual three-dimensional reconstruction could be constructed. Clonality analysis was performed using human androgen receptor gene methylation assay.

RESULTS

Blood vessels show significant connectivity with a Euler number of 2, whereas macrophage clusters exhibited no connectivity. The fibroblast foci showed a high level of interconnection with Euler numbers ranging from 19 to 39. The computer generated three-dimensional models provide a visual confirmation of this connectiveness. Human androgen receptor gene methylation assay analysis of the foci showed balanced methylation consistent with polyclonality.

CONCLUSIONS

The fibroblast foci of UIP are the leading edge of a complex reticulum that is highly interconnected and extends from the pleura into the underlying parenchyma. It is a reactive, rather than a malignant, process.

Expression of the developmental Sonic hedgehog (Shh) signalling pathway is up-regulated in chronic lung fibrosis and the Shh receptor patched 1 is present in circulating T lymphocytes

During pulmonary development, Sonic hedgehog (Shh) and transforming growth factor beta1 (TGF-beta1) signalling both contribute to branching morphogenesis. In interstitial lung disease, the complex alveolar structure of the lung is disrupted and remodelled, which leads to fibrosis, loss of respiratory surface, morbidity, and mortality. It is well documented that TGF-beta1 is involved in fibrosis. However, little is known about Shh signalling in damaged epithelia. This study examined whether or not components of the Shh signalling pathway, as well as TGF-beta1, are expressed in human fibrotic lung disease (cryptogenic fibrosing alveolitis and bronchiectasis) and in murine experimental models of fibrotic and non-fibrotic chronic pulmonary inflammation. Using immunohistochemistry, it was observed that Shh, like TGF-beta1, is up-regulated in epithelial cells at sites of fibrotic disease but not non-fibrotic inflammation. The Shh receptor patched was detected in infiltrating mononuclear cells and alveolar macrophages, as well as normal resting peripheral blood T lymphocytes. Neither Shh nor patched is expressed by hyperproliferative goblet cells in inflammatory epithelium. This study demonstrates that patched is present in human peripheral CD4 and CD8 lymphocytes at both protein and mRNA levels. Taken together, these results suggest that components of the highly conserved Shh signalling pathway may play a role in the remodelling of damaged pulmonary epithelium and that damaged epithelium and cells of the immune system may communicate via this pathway.

The appearance of S-100 protein-positive dendritic cells and the distribution of lymphocyte subsets in idiopathic nonspecific interstitial pneumonia

Idiopathic interstitial pneumonia (IIP) is a progressive interstitial lung disease of unknown etiology. We investigated dendritic cells in idiopathic nonspecific interstitial pneumonia (NSIP) immunohistochemically, using anti-S-100 protein antibody and anti-HLA-DR antibody and also evaluated the relationship between the distribution of S-100 protein-positive dendritic cells (S- 100 DCs) and the lymphocytic subsets in the lung tissue of NSIP. Fifteen patients with the pathological diagnosis of idiopathic NSIP and six patients with usual interstitial pneumonia (UIP) were recruited into this study. Many S-100 DCs were observed in all the cases of idiopathic NSIP but S-100 DCs were not recognized in UIP cases invariably. In the mirror section method, most S-100 DCs showed a positive reaction of anti-HLA-DR antibody but a negative reaction for anti-CD1a antibody. CD8 and CD4 positive lymphocytes were infiltrated diffusely around S-100 DCs. It was demonstrated that the infiltration of CD8 positive lymphocytes predominated in the fibrosing areas and lymphoid follicles around S-100 DCs more so than CD4 positive lymphocytes.We speculate that the pathogenesis of NSIP is different from UIP and that DC and T cell-mediated immune mechanisms may play a role in the development and perpetuation of NSIP.

Autoantibodies in cryptogenic fibrosing alveolitis

The pathogenesis of cryptogenic fibrosing alveolitis (CFA) involves injury, an immune/inflammatory response and fibrosis. The cause of the injury is unknown, but the identification of serum autoantibodies makes an autoimmune aetiology attractive. The core study on which this commentary is based used novel cloning and serum screening technologies in order to identify new public and private autoantibodies in sera from 12 patients with CFA. Largely negative conclusions were drawn from that study. However, we suggest that the prevalence of autoantibodies may have been underestimated, that the study was timely and that this approach is worth pursuing further.

Upregulation of tenascin and TGFbeta production in a type II alveolar epithelial cell line by antibody against a pulmonary auto-antigen

Type II alveolar epithelial cells express a 70-90 kDa antigen to which circulating auto-antibodies have been previously identified in patients with cryptogenic fibrosing alveolitis (CFA). In vitro experiments have been conducted with a rabbit polyclonal antibody raised to this auto-antigen, and the type II epithelial cell line A549. This study examined possible effects that interaction of this antibody with type II epithelial cells might have on the production of cytokines and extracellular matrix components that may be important in the pathogenesis of CFA. There was a significant increase in TGFbeta and tenascin, but not IL4, production by the A549 cells after culture with the immune serum. Further experiments showed that after 72 hours in culture, the antibody decreased A549 cell number in a complement-dependent process, which appeared to be cytostatic rather than cytolytic. These results indicate in vitro biological activity for this antibody and suggest a possible in vivo role for auto-antibody to type II epithelial cells in the pathogenesis of CFA.

Private specificities can dominate the humoral response to self-antigens in patients with cryptogenic fibrosing alveolitis

BACKGROUND

The pathogenetic mechanisms that underlie the interstitial lung disease cryptogenic fibrosing alveolitis (CFA) may involve an immunological reaction to unidentified antigens in the lung, resulting in tissue damage.

METHOD

In order to identify the range of target autoantigens, we used expression cloning, employing serum from an index patient as the probe against an expressed cDNA library that was derived from a tumour cell line. We screened over 5 x 105 recombinants and obtained sequence information on three antigens that had provoked strong responses with immunoglobulin heavy chain class switching, presumably as a consequence of T-cell recognition.

RESULTS

All of the antigens were identifiable by comparison with sequence data from the US National Center for Biotechnology Information. Alanyl tRNA synthetase (ATS) was picked on six occasions; five of these incidences reflected independent recombination events, indicating that the library was not biased. Antibodies to ATS (anti-PL-12) represent the most common reactivity that defines the antisynthetase syndrome, which is typically expressed as polymyositis, dermatomyositis and interstitial lung disease (ILD). The index patient never showed symptoms other than those associated with alveolitis, even though sera obtained from him over a period of 2 years contained antibodies with the same specificity. Autoantibodies to ATS were never detected in serial bleeds from 11 other patients with CFA, and neither did we detect antibodies to the other two antigens identified from the serum of the index patient.

CONCLUSION

The humoral response in patients with CFA can be dominated by autoantibodies with private specificities. This suggests that the antibodies are epiphenomenal and are a secondary feature of tissue damage induced by some other mechanism.

Interstitial lung disease in polymyositis and dermatomyositis

Interstitial lung disease (ILD) is common in patients with polymyositis (PM) and dermatomyositis (DM), and is a major cause of morbidity. Although its cause is unknown, it is known to be closely associated with autoimmune disorders. Its manifestation has been found to be quite heterogeneous, as demonstrated by the differences among PM/DM patients in their immunologic profiles and histopathologic findings, which suggest variations in immunopathogenetic mechanisms. We review the clinicopathologic and immunologic findings in ILD associated with PM/DM, and discuss recent advances in classification, autoantibodies, and treatment. The most critical issues are to clarify the immunopathogenesis of severe forms of ILD, such as rapidly progressive ILD associated with amyopathic DM, and to establish the most appropriate therapy.

Detection of anti-cytokeratin 8 antibody in the serum of patients with cryptogenic fibrosing alveolitis and pulmonary fibrosis associated with collagen vascular disorders

BACKGROUND

It has been suggested that the humoral immune system plays a role in the pathogenesis of cryptogenic fibrosing alveolitis (CFA). Although circulating autoantibodies to lung protein(s) have been suggested, none of the lung proteins have been characterised. The purpose of this study was to determine the antigen to which the serum from patients with pulmonary fibrosis reacted.

METHODS

The anti-A549 cell antibody was characterised in a patient with CFA using Western immunoblotting and immunohistochemical staining of A549 cells. As we identified that one of the antibodies against A549 cells was anti-cytokeratin 8, the expression of mRNA of cytokeratin 8 in A549 cells was evaluated. In addition, we attempted to establish an enzyme linked immunosorbent assay to measure the levels of anti-cytokeratin 8 antibody in the serum of patients with CFA and pulmonary fibrosis associated with collagen vascular disorders (PF-CVD).

RESULTS

Initially two anti-A549 cell antibodies were detected in the serum of patients with pulmonary fibrosis, one of which was characterised as anticytokeratin 8 antibody by Western immunoblotting. We were able to establish an ELISA to measure anti-cytokeratin 8 antibody and found significantly higher levels in patients with CFA and PF-CVD than in normal volunteers, patients with sarcoidosis, pneumonia, and pulmonary emphysema.

CONCLUSIONS

One of the anti-A549 cell antibodies in the serum of patients with CFA was against cytokeratin 8. The serum levels of anti-cytokeratin 8 antibody were increased in patients with CFA and PF-CVD. These results suggest that anticytokeratin 8 antibody may be involved in the process of lung injury in pulmonary fibrosis.

In search of a cause of cryptogenic fibrosing alveolitis (CFA): one initiating factor or many?

The history of patients with idiopathic pulmonary fibrosis (IPF) shows that the disease may be preceded by a viral-like illness. Although viruses have not been demonstrated, it is possible that viruses were not detected in culture because they do not replicate during latency. We investigated the presence of adenovirus in IPF and interstitial pneumonia associated with collagen vascular disease (CVD-IP), using the nested polymerase chain reaction (PCR) and in situ hybridization (ISH) for the E1A region of the adenovirus genome. Studies were performed on lung tissues obtained by transbronchial lung biopsy from 19 patients with IPF, 10 patients with CVD-IP and, for comparison, 20 patients with sarcoidosis. The E1A DNA was present in 3 out of 19 (16%) cases of IPF, in 5 of 10 (50%) cases of CVD-IP, and in 2 of 20 (10%) cases of sarcoidosis. The incidence of E1A DNA in CVD-IP was significantly higher than that in sarcoidosis (p < 0.05). In patients with IPF and CVD-IP, E1A DNA was more prevalent in patients treated with corticosteroids (6 out of 9 cases; 67%) than in those without it (2 out of 20 cases; 10%) (p < 0.01). ISH studies showed that 1 out of 8 cases of IPF and CVD-IP, in which E1A DNA was detected by PCR, was positive for E1A DNA. We conclude that adenovirus E1A is unlikely to be aetiologically involved in the pathogenesis of idiopathic pulmonary fibrosis or interstitial pneumonia associated with collagen vascular disease. However, a latent adenovirus infection may be reactivated or may newly infect the host following corticosteroid administration.

Immunodeficiency of aging

Aging is associated with declines in multiple areas of immune function, but to date no single mechanism has emerged as being responsible for all the observed changes. Many changes occur at different rates within individuals as well as between individuals. With advancing age there is a concomitant increase in the incidence of many infections and cancers. It is being increasingly acknowledged that autoimmune processes play a proinflammatory role in the development of many pathological conditions, such as atherosclerosis. However, direct causal relationships between specific changes in immunity and the occurrence of specific diseases are rare. There is accumulating epidemiological, in vivo and in vitro evidence to support many such direct relationships in both animals and humans. It is likely that the mechanisms underlying age-related changes in immunity are multifactorial, with both genetic and environmental factors playing a significant role. Despite the current lack of unifying theories, much active and exciting work is proceeding in the area of immune stimulation. Studies describing age-related changes in immunity, as well as the testing of interventions to reverse these changes, will continue to fill the gaps in our knowledge, leading to a more comprehensive understanding of immunosenescence.

The pathogenesis of pulmonary fibrosis: is there a fibrosis gene?

Interstitial fibrosis is seen in the lung in response to a variety of insults, and often appears stereotypical in terms of its clinical and pathological features. However, exposure to a known aetiological factor does not always lead to fibrosis. For example in bleomycin-induced pulmonary fibrosis, a wide variation in response is seen both in humans and in animal models, which is not completely accounted for by known risk factors. These observations and the existence of a number of familial forms of lung fibrosis suggest a genetic predisposition. Current hypotheses concerning the pathogenesis of pulmonary fibrosis propose an initial stage involving the influx of inflammatory cells into the interstitium. These cells, together with activated resident cells are then thought to release polypeptide mediators that stimulate the fibroblast proliferation and matrix protein synthesis typical of these disorders. Genetic influences could have an important role in regulating a number of these events, altering the immunological response to injury or modulating collagen metabolism in the lung. However, despite recent advances in molecular genetic techniques, there have been few human studies to date. Most have concentrated on genetic loci with a high degree of polymorphism such as the human leucocyte antigen (HLA) system and yield conflicting results. Others offer tantalising but as yet, incomplete insights into the mechanisms involved. Defining the genetic abnormalities underlying both the familial forms of pulmonary fibrosis and the variations seen in response to lung injury should enhance our understanding of the pathogenic processes and help to focus research in this area.

The immunological architecture of B-lymphocyte aggregates in cryptogenic fibrosing alveolitis

Cryptogenic fibrosing alveolitis (CFA) is believed to have a pathogenesis mediated by the cellular arm of the immune system. Previous studies have, however, indicated the presence of B-lymphocyte aggregates, as well as evidence of local immunoglobulin production and increased levels of B-cell growth factors. It has recently been shown that CFA is associated with the production of circulating IgG autoantibodies to antigen(s) associated with alveolar lining cells. This prompted an examination of the immunological architecture of the B-lymphocyte aggregates, in order to assess whether they might provide histological confirmation of a local humoral immune response in these patients. Thirty-eight consecutive open lung biopsy specimens were examined from patients with CFA and aggregates of B lymphocytes were identified in 37/38. In only five cases were germinal centres seen. The morphological appearances of the aggregates were reminiscent of those observed in mucosal associated lymphoid tissue (MALT). Using immunohistochemistry, despite the low frequency of true germinal centre formation, the B-lymphocyte aggregates were shown to contain the cellular micro-environment necessary for a humoral immune response. In addition, there was evidence of lymphocyte proliferation and activation within these aggregates. These results provide evidence of a local humoral immune response associated with B-lymphocyte aggregates in the lungs of patients with CFA.

A type 2 (Th2-like) pattern of immune response predominates in the pulmonary interstitium of patients with cryptogenic fibrosing alveolitis (CFA)

CFA is an inflammatory condition of the lungs resulting in scarring, pulmonary failure and death. The etiology of the disease is unknown, but the pathogenesis is believed to involve a persistent immunological reaction to unidentified antigen in the lung resulting in tissue damage. Recent advances in our understanding of the immune system have shown that different patterns of stimulatory cytokines are produced at sites of inflammation by a range of cell types. Patterns of cytokine reproduction by inflammatory cells are recognized to be associated with different patterns of immunological response, and these have been described as type 1 (or Th1-like) and type 2 (or Th2-like) on this basis. We have studied cytokine expression in the intestinal inflammatory cell infiltrate in lung tissue from patients with CFA using mRNA in situ hybridization and immunohistochemistry. Our results show that while there is evidence for both a type 1 (characterized by interferon-gamma (IFN-gamma) and type 2 (characterized by IL-4 and IL-5) response present in CFA, the type 2 (or Th2) pattern of cytokines appears to predominate. This would be consistent with a possible role for the humoral immune response in the pathogenesis of this condition. In addition, recent evidence suggests that IL-4 and IFN-gamma may be important regulatory factors for pulmonary fibroblasts. The relative paucity of IFN-gamma may contribute to the excessive fibroblast activation, deposition of collagen and scar formation that occurs in CFA.

Tenascin immunoreactivity in cryptogenic fibrosing alveolitis

Tenascin is a hexameric extracellular matrix (ECM) glycoprotein which has been demonstrated to have a temporal relationship with active scar formation in adult tissues. We hypothesized that this ECM protein might therefore serve to identify areas of active scarring in lung biopsies from patients with cryptogenic fibrosing alveolitis (CFA). The distribution of tenascin was examined in open lung biopsies from ten patients with CFA, six patients with sarcoidosis, and six pulmonary resection specimens from patients with no evidence of interstitial lung disease, using an immunohistochemical technique. Immunoreactive tenascin was not identified in histologically normal control lung parenchyma and was only focally found around large aggregates of granulomas in sarcoidosis. In the CFA, tenascin production was demonstrated in minimally damaged alveolar walls and areas of active disease but not in end-stage scarred lung. There was considerable local heterogeneity of staining within cases, which did not appear to relate to the density of the local inflammatory infiltrate. Large plaques of tenascin were noted to be particularly associated with hyperplastic type II alveolar epithelial lining cells, which are recognized to produce fibrogenic cytokines. The examination of tenascin expression in open lung biopsies from patients with CFA may be useful in assessing fibrogenic activity and may thus provide additional prognostic information.