Natural Autoreactive B Cells in Transgenic Mice Reproduce an Apparent Paradox to the Clonal Tolerance Theory

Systemic autoimmune diseases are characterized by the production of high titer autoantibodies specific for ubiquitous nuclear self-Ags such as DNA, Sm, and La (SS-B), so the normal mechanisms of B cell tolerance to disease-associated nuclear Ags have been of great interest. Mechanisms of B cell tolerance include deletion, anergy, developmental arrest, receptor editing, and B cell differentiation to the B-1 subtype. However, recent studies in our laboratory have suggested that B cell tolerance to the nuclear autoantigen La is limited in normal mice, and tolerance may reside primarily in the T cell compartment. To test this hypothesis, we created Ig transgenic mice expressing the IgM H chain from an mAb specific for a xenogeneic epitope within human La (hLa). These mice were bred with hLa-transgenic mice that constitutively express hLa in a manner comparable to endogenous mouse La. Between 5–15% of transgenic B cells developing in the absence of hLa were specific for hLa, and these cells were neither depleted nor developmentally arrested in the presence of endogenous hLa expression. Instead, these autoreactive B cells matured normally and differentiated into Ab-forming cells, capable of secreting high titer autoantibody. Additionally, the life span of autoreactive hLa-specific B cells was not reduced, and they were phenotypically and functionally indistinguishable from naive nonautoreactive hLa-specific B cells developing in the absence of hLa. Together these data suggest a lack of intrinsic B cell tolerance involving any known mechanisms indicating that these autoreactive B cells are indifferent to their autoantigen.

Section: Anti-hla B Cells and Clonal Ignorancesupporting

confidence: 79%

Tolerance through Indifference: Autoreactive B Cells to the Nuclear Antigen La Show No Evidence of Tolerance in a Transgenic Model

Aplin

Keech

Kauwe

et al. 2003

“…The RF transgenic mice expressing H and L chain genes encoding the chimeric murine-human nAAb bearing the G6 V H Id and the 17109 V Id have been previously described (27). Briefly, founder lines were maintained by backcross mating with the C57BL/6 strain.…”

Section: Micementioning

confidence: 99%

“…Cells were prepared from bone marrow, spleen, and peritoneum, then stained as described (27). Cell phenotype was determined using the following reagents: anti-mouse B220 FITC, anti-mouse …”

Section: Flow Cytometry Analysismentioning

confidence: 99%

“…For this reason, we have generated Tg mice that express a prototypical human nAAb that reacts with different self-Ags, including ssDNA and human IgG (rheumatoid factor (RF) activity), but not with murine IgG. We have previously shown that, in the absence of constitutive expression of human IgG, these nAAb-producing B cells develop normally on a nonautoimmune background, without being anergic (27). Indeed, it was not possible, in these mice, to determine the role, if any, of ssDNA in the maturation of the Tg B cells.…”

mentioning

confidence: 99%

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B Cell Positive Selection by Soluble Self-Antigen

Julien

Soulas

Garaud

et al. 2002

Self Cite

It is well established that autoreactive B cells undergo negative selection. This stands in paradox with the high frequency of so-called natural autoreactive B cells producing low affinity polyreactive autoantibodies with recurrent specificities, suggesting that these B cells are selected on the basis of their autoreactivity. We previously described two transgenic mouse lines (with and without IgD) producing a human natural autoantibody (nAAb) that binds ssDNA and human Fcγ. In the absence of human IgG, nAAb-transgenic B cells develop normally. By crossing these mice with animals expressing knockin chimeric IgG with the human Fcγ, we now show that the constitutive expression of chimeric IgG promotes the increase of nAAb-expressing B cells. This positive selection is critically dependent on the presence of IgD, occurs in the spleen, and concerns all mature B cell subsets, with a relative preferential enrichment of marginal zone B cells. These data support the view that soluble self-Ags can result in positive clonal selection.

“…Also, several recent studies have indicated that some autoreactive B cells complete peripheral development harboring no obvious proliferative or differentiative defects, suggesting that they do not functionally interact with their cognate autoantigen(s). Such B cells are often referred to as being in an "ignorant" or "indifferent" state (12,33). These observations suggest that the presence of autoreactive B cells in the periphery poses a significant risk factor for the development of autoimmune disease.…”

mentioning

confidence: 98%

Antinuclear Antigen B Cells That Down-Regulate Surface B Cell Receptor during Development to Mature, Follicular Phenotype Do Not Display Features of Anergy In Vitro

Liu

Manser

2005

We previously demonstrated that B cells expressing a transgenic BCR with “dual reactivity” for the hapten arsonate and nuclear autoantigens efficiently complete development to follicular phenotype and stably reside in follicles in vivo. These B cells express very low levels of surface IgM and IgD, suggesting that they avoid central deletion and peripheral anergy by reducing their avidity for autoantigen via surface BCR (sBCR) down-regulation. Since a variety of states of B cell anergy have been previously described, a thorough examination of the functional capabilities of these B cells was required to test this hypothesis. In this study, we show that surface Ig cross-linking induces amounts of proximal BCR signaling in these B cells commensurate with their reduced sBCR levels. Functionally, however, they are comparable to nonautoreactive B cells in cell cycle progression, up-regulation of activation and costimulatory molecules, and Ab-forming cell differentiation when treated with a variety of stimuli in vitro. In addition, these B cells can efficiently process and present Ag and are capable of undergoing cognate interaction with naive TCR-transgenic T cells, resulting in robust IL-2 production. Together, these data reveal a lack of intrinsic anergy involving any known mechanism, supporting the idea that this type of antinuclear Ag B cell becomes indifferent to cognate autoantigen by down-regulating sBCR.