Germinal center exclusion of autoreactive B cells is defective in human systemic lupus erythematosus
Amedeo Cappione III, Jennifer H. Anolik, Aimee Pugh-Bernard, Jennifer Barnard, Paul Dutcher, Gregg Silverman, Iñaki Sanz
Amedeo Cappione III, Jennifer H. Anolik, Aimee Pugh-Bernard, Jennifer Barnard, Paul Dutcher, Gregg Silverman, Iñaki Sanz
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Research Article Autoimmunity

Germinal center exclusion of autoreactive B cells is defective in human systemic lupus erythematosus

Abstract

Breach of B cell tolerance is central to the pathogenesis of systemic lupus erythematosus (SLE). However, how B cell tolerance is subverted in human SLE is poorly understood due to difficulties in identifying relevant autoreactive B cells and in obtaining lymphoid tissue. We have circumvented these limitations by using tonsil biopsies to study autoreactive B cells (9G4 B cells), whose regulation is abnormal in SLE. Here we show that 9G4 B cells are physiologically excluded during the early stages of the GC reaction before acquiring a centroblast phenotype. Furthermore, we provide evidence to indicate that an anergic response to B cell receptor stimulation may be responsible for such behavior. In contrast, in SLE, 9G4 B cells progressed unimpeded through this checkpoint, successfully participated in GC reactions, and expanded within the post-GC IgG memory and plasma cell compartments. The faulty regulation of 9G4 B cells was not shared by RA patients. To our knowledge, this work represents the first comparative analysis of the fate of a specific autoreactive human B cell population. The results identify a defective tolerance checkpoint that appears to be specific for human SLE.

Authors

Amedeo Cappione III, Jennifer H. Anolik, Aimee Pugh-Bernard, Jennifer Barnard, Paul Dutcher, Gregg Silverman, Iñaki Sanz

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Analysis of 9G4 cells in healthy spleens. (A) CD19+ spleen B cells were ...
Analysis of 9G4 cells in healthy spleens. (A) CD19+ spleen B cells were analyzed with IgD, CD38, CD27, and 9G4 antibodies as described above (n = 7 spleens). 9G4 B cells are very scarce within the GC and post-GC compartments (IgG and IgA memory). Representative results are shown as histograms. (B) Staining for IgM, IgD, CD21, and CD23 expression identified transitional (T1 and T2), follicular (FO), and MZ populations with a distribution similar to mouse B cells (12, 69). We identified an additional fraction composed of significant numbers of IgD+ cells, which represents a distinct subset of IgD+ MZ B cells (MZ*) (19). (C) Total spleen B cells were fractionated into MZ and follicular subsets as described above and further analyzed for the frequency of 9G4 B cells. The frequency of spleen follicular 9G4 cells was similar to the tonsil, and a lower but significant frequency was observed in the MZ fraction. (D) The majority of total and 9G4 MZ B cells express CD27. (E) The dearth of IgG and IgA 9G4 B cells was consistently documented in the spleen whether using total B cells or fractionated MZ B cells. (F) Dot plot analysis of total and 9G4 spleen B cells demonstrated that the vast majority of 9G4 B cells express an IgM+IgD+ phenotype. (G) Within the naive compartment, 9G4 B cells express significantly lower levels of surface IgM. MFI, mean fluorescence intensity.