SUMMARYThere are three classes of RNA polymerase enzyme (RNAPs I, II and III). In systemic sclerosis (SSc), three main groups of anti-RNAP sera have been characterized by radioimmunoprecipitation techniques: anti-RNAP I/III sera, anti-RNAP I/II/III sera, and a group precipitating both RNAP II and topoisomerase I (topo I). Some sera in this third group precipitate the phosphorylated (IIO) form of RNAP II in the absence of the unphosphorylated (IIA) form. Certain other antinuclear antibodies (ANA) have also been detected in anti-RNAP IIO/IIA/topo I and anti-RNAP IIO/topo I sera. In the present study of 155 SSc patients, clinical features of individuals from each of these antibody groups were assessed and compared with those of patients from other autoantibody-defined groups. The anti-RNAP I/II/III antibody specificity was closely associated with the presence of diffuse cutaneous SSc (dc-SSc) (77·8%; cf. remaining group, 12·4%; P < 0·001; relative risk (RR) 6·3). Patients with anti-RNAP I/III antibodies also had an increased incidence of dc-SSc, but this was not significant (42·9%; cf. remainder, 15·7%). Anti-RNAP þ patients had a significantly increased incidence of renal involvement (29·0%, cf. remainder, 11·3%; P < 0·05; RR 2·6), with 40% of anti-RNAP I/II/III patients having renal disease. Meanwhile, the presence of anti-centromere antibodies (ACA) was associated with limited cutaneous SSc (lc-SSc) (100·0%; cf. remainder, 75·3%; P < 0·005), together with reduced incidences of both renal disease (2·4%, cf. remainder, 22·1%: P < 0·01) and pulmonary fibrosis (21·4%, cf. remainder, 52·3%; P < 0·005; RR 1·9). Anti-topo I antibodies were associated with the presence of pulmonary fibrosis (69·7%; cf. remainder, 32·6%; P < 0·001; RR 2·1). A majority of anti-topo I sera were from lc-SSc patients, regardless of whether anti-topo I antibodies occurred alone (75·0%) or together with anti-RNAP IIO þ IIA antibodies (75·0%), and this was similar to the remainder (86·5%; NS). However, when anti-topo I þ patients were compared with the ACA group, and then with all anti-RNAP I þ patients (37·5% lc-SSc), significant differences were found in the occurrence of dc-versus lc-SSc (P < 0·005 and P < 0·05, respectively). In conclusion, these results confirm that there are three main groups of SSc sera, each characterized by the presence of a mutually exclusive SSc-specific autoantibody (ACA, anti-topo I or anti-RNAP I), and distinguished by patterns of cutaneous involvement and specific clinical features. It appears that, in each of the three groups of SSc patients, distinct pathological processes are occurring, which are responsible for the characteristic symptoms, for the modification of particular autoantigens and, consequently, for the production of particular autoantibodies. Based on these data, together with our previous results, it is further hypothesized that anti-RNAP II antibodies may be produced in the context of two different immune response pathways.

Aims-To develop a multiplex polymerase chain reaction (PCR) for the simultaneous detection of Mycoplasma pneumoniae, Chlamydia pneumoniae, and Chlamydia psittaci in respiratory samples. Methods-Oligonucleotide primers for the amplification of the DNA of these three organisms were optimised for use in combination in the same reaction. PCR products were detected by hybridisation with pooled internal probes using an enzyme linked immunosorbent assay. Those with positive signals were further diVerentiated using species specific probes. Quality of DNA extraction and PCR inhibition were controlled by amplification of a human mitochondrial gene. A panel of 53 respiratory samples with known results was evaluated blindly. This was followed by a retrospective study on sputa collected from 244 patients with suspected community acquired pneumonia. Results-The multiplex assay had a lower sensitivity than PCR with individual primers by about one log. The resultant sensitivity was considered acceptable for diagnostic use. Of the panel of 53 samples, nine of 11 M pneumoniae, 11 of 11 C pneumoniae, six of seven C psittaci, and 24 of 24 negative samples were correctly identified. Of the 244 patients with pneumonia, seven (2.9%) had detectable M pneumoniae, six (2.5%) had C pneumoniae, and one (0.4%) had C psittaci. The case notes from 11 patients were studied. The PCR finding was of possible significance in at least eight of these patients. Conclusions-This multiplex PCR assay has the potential to be used as a diagnostic and epidemiological tool. Further prospective studies are needed to establish its clinical value. (J Clin Pathol 1999;52:257-263) Keywords: atypical pneumonia; polymerase chain reaction; Mycoplasma pneumoniae; Chlamydia pneumoniae; Chlamydia psittaci Mycoplasma and chlamydia are major causes of community acquired atypical pneumonia.

Objective. To determine the frequency and type of autoantibodies present in patients with systemic sclerosis (SSc) associated with an established environmental toxin. Methods. Clinical data and sera were available from 14 men with silica‐associated SSc who had developed SSc after at least 2 years of exposure to silica at work. Controls included 27 men with silicosis without SSc. Autoantibodies were measured by immunodiffusion, immunoblotting, and functional inhibition of topoisomerase I (topo I). Results. Nine of the 14 patients with silica‐associated SSc had anti—topo I antibodies. All anti—topo I antibodies in the patients with silica‐associated SSc and in 14 anti—topo I—positive patients with idiopathic SSc were directed at an active site of topo I, or at least sterically inhibited its function. One patient with silica‐associated SSc had anticentromere antibodies. Unexpectedly, 2 patients with silicosis who had no symptoms of a connective tissue disease had autoantibodies to Ro/SS‐A and La/SS‐B autoantigens. Conclusion. Anti—topo I antibodies are the predominant autoantibodies present in silica‐associated SSc. The generation of anti—topo I antibodies in genetically susceptible individuals may depend partly on the patient's sex and on the site of organ involvement, and may be triggered by silica particles acting as an immune adjuvant.

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