A REVIEW OF IMMUNOFLUORESCENT PATTERNS ASSOCIATED WITH ANTINEUTROPHILCYTOPLASMIC ANTIBODIES (ANCA) AND THEIR DIFFERENTIATION FROM OTHER ANTIBODIES

Aim-To describe the neutrophil fluorescent patterns produced by antine utrophil cytoplasmic antibodies (ANCA) with different antigen specific ities, and by other auto- and alloantibodies. Background-Most sera fro m patients with active generalised Wegener's granulomatosis result in diffusely granular cytoplasmic neutrophil fluorescence with internucle ar accentuation (cANCA) and proteinase 3 (PR3) specificity. About 80% of the sera from patients with microscopic polyangiitis result in peri nuclear neutrophil fluorescence with nuclear extension (pANCA) and mye loperoxidase (MPO) specificity, or a cANCA pattern with PR3 specificit y. However, many different neutrophil fluorescence patterns are noted on testing for ANCA in routine immunodiagnostic laboratories. Methods- Sera sent for ANCA testing, or containing a variety of auto- and alloa ntibodies, were studied. They were examined by indirect immunofluoresc ence according to the recommendations of the first international ANCA workshop, and for PR3 and MPO specificity in commercial and in-house e nzyme linked immunosorbent assays (ELISA). Results-Sera with typical c ANCA accounted for only half of all neutrophil cytoplasmic fluorescenc e. Other sera had ''flatter'' fluorescence without internuclear accent uation, and the corresponding antigens included MPO and bactericidal/ permeability increasing protein (BPI), but were usually unknown. Perip heral nuclear fluorescence without nuclear extension occurred typicall y when the antigens were BPI, lactoferrin, lysozyme, elastase, or cath epsin G. Most types of ANA were evident on ethanol fixed neutrophil nu clei. AntidsDNA, antiRo, and antilamin antibodies resembled pANCA. Ant imicrobial and antiribosomal antibodies produced cytoplasmic fluoresce nce, and antiGolgi antibodies, a pANCA. Sera from patients with anti-s mooth muscle antibodies were associated with cytoplasmic fluorescence. There was no neutrophil fluorescence with anti-skeletal muscle and an ti-heart muscle antibodies, anti-liver/kidney microsomal, antithyroid microsomal, or antiadrenal antibodies. Alloantibodies such as antiNB1 typically resulted in cytoplasmic fluorescence of only a subpopulation of the neutrophils. Conclusions-The ability to distinguish between di fferent neutrophil fluorescence patterns, and the patterns seen with o ther auto- and alloantibodies is helpful diagnostically. However, the demonstration of MPO or PR3 specificity by ELISA will indicate that th e neutrophil fluorescence is probably clinically significant, and that the diagnosis is likely to be Wegener's granulomatosis or microscopic polyangiitis.