Structural analysis of human antibodies to proteinase 3 from patients with Wegener granulomatosis

We determined the structure of five IgM autoAbs to proteinase-3 (PR3). These Abs are highly specific for Wegener's granulomatosis (WG) and may be involved in the pathogenesis of vasculitis in WG. Five clonal lymphoblastoid cell lines secreting Abs to PR3 were derived from four patients' B cells. From 3 to 5% of supernatants from wells contained detectable anti-PR3 Abs, indicating that anti-neutrophil cytoplasmic Ab specificity represents a sizable part of the IgM B cell repertoire in patients with WG. Mu heavy chains of WG1, WG4-1, and WG4-2 clones belonged to the VH3 subgroup. WG4-1 and WG4-2 heavy chains were identical, indicating an oligoclonal expansion of autoreactive B cells in this patient. WG4-1 (and WG4-2) used the VH3-23 V(H) gene, the product of which was shown to directly bind PR3. Heavy chains of WG2 and WG3 derived from VH4-59 and VH1-2 genes, respectively. Comparison with germline sequences showed that three of the five V(H) genes from clonal lines were somatically mutated with a R:S ratio in complementarity-determining regions of 3:0, 5:1, and 5:1, respectively. Three kappa light chains derived from the Vkappa4 gene, and one derived from a Vkappa1 gene. In these four Vkappa genes, there were overall R:S ratios of mutation of 8:1 and 0:7 in complementarity-determining regions and framework regions, respectively. These data suggest that the production of these autoantibodies, which are increasingly important in the diagnosis and management of WG, are influenced by an Ag-driven process.