IgM anti-myeloperoxidase antibody-secreting lymphocytes are present in the peripheral repertoire of lupus mice but rarely differentiate into IgG-producing cells

Abstract

SUMMARYTwo IgM, k anti-myeloperoxidase (MPO) monoclonal antibodies, 6D6 and 9B5, bound to MPO in a solid-phase enzyme-linked immunosorbent assay were derived from the splenocytes of (NZB × NZW) F1 and MRL/lpr-lpr mice, respectively. 6D6 gave a characteristic perinuclear immunofluorescence staining pattern on ethanol-fixed human neutrophils, bound to the native form of MPO by immunoblotting and had a high constant affinity for MPO as demonstrated by real-time specific interaction. 9B5 produced a cytoplasmic immunofluorescence staining pattern, reacted with the heavy chain of MPO and had a low constant affinity for MPO. The heavy-and light-chain variable region genes of monoclonal antibodies (mAb) 6D6 and 9B5 were sequenced and found to be highly homologous to germline genes and to contain negatively charged amino acids in the complementarity determining regions. IgM MPO-binding activity was observed in most BW and MRL/lpr-lpr mouse sera, which may correspond to polyclonal activation of B cells, whereas IgG anti-MPO antibodies could be rarely detected. Thus, this study indicates that (i) BW and MRL/lpr-lpr mice do not delete IgM anti-MPO secreting B cells, do not maintain these B cells in a state of anergy, but most individuals are not able to spontaneously induce the class-switching of this autoantibody population; (ii) IgM anti-MPO antibodies can recognize different epitopes on MPO and produce different immunofluorescence staining pattern on ethanol-fixed human neutrophils, as demonstrated by the immunochemical properties of the two lupus-mouse derived mAb.

Mechanisms of wound healing responses in lupus‐prone New Zealand White mouse strain

“…We undertook these studies of wound healing in NZW mice in light of their susceptibility to develop systemic erythematous lupus‐like (SLE) disease either spontaneously, in aging animals or after being exposed to several environmental challenges and/or internal insults 9 . This condition, SLE, is a polygenic systemic autoimmune disease characterized by the production of a variety of autoantibodies that interact with endogenous antigens favoring widespread inflammatory injury 9–12 . This genetic trait (auto‐immune disease) in one mouse strain (MRL/+) has been shown to determine an aberrant wound healing phenotype with accelerated closure of ear punch injuries, increased heart revascularization after cryo‐injury, and rapid wound healing of alkali‐burned cornea 6,8,9 .…”

“…The New Zealand White or Black mouse strains (NZW, NZB) also represent a model for systemic lupus erythematosus (SLE), a disease characterized by multi‐phenotypic inflammatory manifestations in a variety of organs and tissues (skin, joints, kidney). When these mice are bred to several other strains (NZB, BXSB, B6.Sle1, B6.Yaa) the F 1 hybrid develops severe lupus glomerulonephritis, coronary vascular disease, altered tissue levels of angiogenic factors (VEGF, TNF‐α), antibodies to inflammatory enzymes such as myeloperoxidase (MPO) and accelerated mortality 10–12 . NZW mice themselves are normally clinically healthy, but they still present subclinical features of SLE such as nephritis, increased susceptibility to environmental insults 10 and to immune‐mediated end‐organ damage 13 .…”

Maintenance of Tolerance by Regulation of Anti-myeloperoxidase B Cells

“…Although several of the heavy chains from V1C-J5 Tg hybridomas expressed the J558 variable region gene, the number of hybridomas examined was too small to ascertain whether there is a restriction in heavy-chain variable region gene use by anti-MPO B cells. Of note, one of the non-Tg light chains, V12-41, expressed by hybridomas from our V1C-J5 Tg mice, is also expressed by another anti-MPO antibody produced by NZB ϫ NZW mice, 23 We examined the B cell repertoire to elucidate further the mechanisms of maintaining tolerance to MPO in this nonautoimmune mouse model. We observed Ͼ85% fewer B cells in the bone marrow of Tg mice, in part because of reduced clonal expansion at the pre-B cell stage as a result of expression of the light-chain transgene.…”

Antineutrophil cytoplasmic antibody (ANCA)-associated autoimmune diseases induced by antithyroid drugs: comparison with idiopathic ANCA vasculitides

“…IgM anti-MPO antibody-secreting lymphocytes are present in the peripheral repertoire of lupus-prone mice but rarely differentiate into IgG-producing cells [39]. We can suppose that ATDs induce production of the potentially pathogenic MPO-ANCA IgG 4 subclass [40].…”

“…We can suppose that ATDs induce production of the potentially pathogenic MPO-ANCA IgG 4 subclass [40]. MPO has the characteristics of a SLE-related antigen [39]. MPO-ANCA in SLE is most often found in the context of secondary APS [41], for which there were no criteria in our patients.…”