Clinical and experimental immunology
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Clin. Exp. Immunol. · Aug 1997
Comparative StudyHuman mast cells expressing recombinant proteinase 3 (PR3) as substrate for clinical testing for anti-neutrophil cytoplasmic antibodies (ANCA).
We have expressed conformationally intact, enzymatically active recombinant PR3 in HMC-1 cells (HMC-1/PR3 cells) that is recognized by C-ANCA. Here we directly compared the clinical utility of C-ANCA testing by indirect immunofluorescence (IIF) using HMC-1/PR3 cell cytospin versus polymorphonuclear neutrophil (PMN) cytospin preparations and commercially available anti-PR3 ELISA kits. Two hundred sera were tested independently by three investigators: 101 previously determined to be C-ANCA-positive by routine clinical laboratory testing using standard IIF on PMN cytospins, and 99 control samples chosen primarily because they contained antibodies against other cytoplasmic target antigens. ⋯ IIF using HMC-1/PR3 cells was as sensitive as the most sensitive anti-PR3 ELISA (79.8% versus 80.7%, P = 0.739), and more sensitive than standard IIF C-ANCA testing using PMN cytospins (79.8% versus 75.2%, P = 0.025) or the anti-PR3 ELISA with the least false-positive test results (79.8% versus 63%, P < 0.01). These findings indicate that HMC-1/PR3 cells are a very sensitive antigen-specific substrate for clinical anti-PR3 ANCA testing which appears superior to standard C-ANCA testing using PMN cytospin substrates and anti-PR3 ELISA. Our results also suggest that in WG the C-ANCA fluorescence pattern is not caused by antibodies against target antigens other than PR3.