Table 1.
Methodological criteria for assignment of autoantibodies
| Autoantibody against | Findings classifying patients as antibody-positive | Usual additional findings |
|---|---|---|
| Centromere | Centromeric immunofluorescence pattern on HEp-2 cells (308 of 310 were positive) or a CENP-B band in line assay (309 of 310 positive) | |
| Topoisomerase I | At least two of three findings: Scl-70-positive signal in line assay (258 of 260 positive), a band comigrating with a prototype band in IP (all positive), a line of identity in ID with the Scl-70 prototype serum (244 of 260 positive) | Typical HEp-2 cell immunofluorescence pattern: fine granular karyoplasmic, weakly nucleolar, metaphase chromosome-positive |
| RNA polymerases | Characteristic IP pattern comigrating with the pattern of a prototype serum mainly consisting of four bands: Ia, Ib, IIIa and IIIb [58] | Confirmation by ELISA in 32 of 32 cases with the immunodominant epitope of RNA polymerase III subunit RPC155 according to Kuwana et al. [71], provided by Matritec, Freiburg, Germany. ANA immunofluorescence on HEp-2 cells was predominantly fine granular only sometimes (five cases) in addition nucleolar [72]. |
| Fibrillarin | An IP band (approximately 34 kDa) comigrating with a prototype serum band, plus a nucleolar immunofluorescence pattern on HEp-2 cells | Confirmation by investigational ELISA kindly provided by Euroimmun, Lübeck, Germany, positive in 11 and borderline in 1 of the 12 cases |
| To | An IP band of approximately 40 kDa plus a nucleolar immunofluorescence pattern on HEp-2 cells; confirmation by immunoblot analysis with recombinant To antigen kindly supplied by Dr M Blüthner, Labor Seelig, Karlsruhe, Germany | |
| PM-Scl | A line of identity in ID with a PM-Scl prototype serum (41 of 42 cases) and/or positive result of ELISA with the synthetic peptide PM-1α [73] (Dr Fooke Laboratorien GmbH, Neuss, Germany) (12 of 13 cases) | Positive reaction in 37 of 41 cases for PM-Scl by line assay. ANA immunofluorescence on HEp-2 cells usually was nucleolar plus fine granular karyoplasmic. |
| Ku | Two prominent IP bands at about 70 and 80 kDa comigrating with prototype bands | In 3 of 10 cases, a line identical to a Ku prototype band in ID. ANA immunofluorescence was finely granular, usually at a high titre. |
| U1-RNP | A positive signal for RNP/Sm in line assay, with or without a positive signal for Sm, plus a typical IP pattern consisting of at least antigen A (about 33 kDa), antigen B/B' (about 28/29 kDa) and antigen C (about 22 kDa) | In 37 of 41 cases, a line of identity with a U1-RNP prototype in ID. ANA pattern on HEp-2 cells usually was coarsely speckled. |
| Sm | A positive signal for RNP/Sm as well as for Sm in line assay | In two of four cases, a band identical to a Sm prototype in ID with ribonuclease-digested calf thymus extract. IP and immunofluorescence patterns were similar to those found for anti-U1-RNP. |
| Jo-1 | A positive signal for Jo-1 in line assay plus a band identical to a Jo-1 prototype band in ID | Immunofluorescence on HEp-2 cells was inconsistent. |
| Pl-7 | IP band of about 80 kDa comigrating with prototype band plus a band identical to a Pl-7 prototype band in ID | Cytoplasmic immunofluorescence on HEp-2 cells |
| OJ | Typical triplet band in IP comigrating with prototype bands | Cytoplasmic immunofluorescence on HEp-2 cells |
| U11-RNP [74,75] | An RNP-like IP pattern and coarsely speckled ANA immunofluorescence, without any U1-RNP signals in line assay and ID; U11-RNP specificity detected by C Will and R Lührmann, Marburg, Germany | |
| p25/p23 [76,77] | Doublet IP bands of about 25 and 23 kDa, with the 25 kDa band comigrating with the precipitate of rabbit anti-p25 kindly provided by E Chan, Gainesville, FL, USA | HEp-2 cell immunofluorescence pattern was always centromeric because anti-p25/p23 was exclusively found together with anticentromere. |
| SL | A band identical to the SL prototype band in ID plus an IP band at about 31 kDa comigrating with the precipitate of the SL reference serum | HEp-2 cell immunofluorescence pattern was fine granular, but in this study often was masked because of other coexisting antibodies |
| NOR-90 | Doublet IP bands at about 90 kDa comigrating with the precipitate of a NOR-90 reference serum [78] | The nucleolar immunofluorescence pattern expected on HEp-2 cells was hard to detect in the sera examined in this study, because NOR-90 antibodies in all cases coincided with other autoantibodies visible on HEp-2 cells. |
| Mitochondrial M2 | AMA M2-positive signal by line assay (40 of 41 positive) and/or AMA typical cytoplasmic immunofluorescence on HEp-2 cells and/or rat kidney sections (27 of 41 positive) | In IP, a band of around 70 kDa was present in 36 of 41 cases. |
| Sp100 | Multiple nuclear dot pattern on HEp-2 cells [79] plus Sp100 signal in the line assay HUMAN IMTEC-Liver Line Immunoassay (HUMAN Diagnostics GmbH, Wiesbaden, Germany) | |
| Ro52 | Ro52-positive signal by line assay | |
| Ro60 | Ro60-positive signal by line assay | |
| La | La-positive signal by line assay |
AMA = antimitochondrial antibodies; ANA = antinuclear antibodies; CENP-B = centromere protein B; ID = immunodiffusion; IP = immunoprecipitation; PM-Scl = polymyositis and scleroderma; RNAP = RNA polymerase; RNP = ribonucleoprotein;.