Heterogeneity of ANCA Sera Showing Atypical, Peripheral and Classical Cytoplasmic Immunofluorescence Patterns
Atypical (A) ANCA immunofluorescence (IF) patterns have been described in several disease groups. We have previously reported a distinct cytoplasmic A-ANCA in 7–10% of patients with SLE and/or RA. Here, we show that these rheumatic disease associated A-ANCAs are best identified using U937 cells as substrate and that they do not target either a serine proteinase or a peroxydase. Furthermore, these sera immunoprecipitate a 40 kDa or a 42 kDa band using in vivo 35S-amino acid labelled HL60 or U937 cell extracts, respectively. Although these bands are the only one seen with pure A-ANCA sera, they can also be found in addition to the expected bands of PR3 or MPO in up to 30% of bona fide C- or P-ANCA sera. These data confirm and extend our previous observations. They also suggest that target heterogeneity of ANCA antibodies is frequent. Care should thus be taken in interpreting in a cause and effect relationship, an IF pattern or a biological effect produced by a serum with ill documented monospecificity. The exact nature and significance of this (these) new antigen(s) have yet to be clarified.
KeywordsSystemic Lupus Erythematosus U937 Cell HL60 Cell Cytospin Preparation Human PMNs
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