Dysregulated cytokine production by dendritic cells modulates B cell responses in the NZM2410 mouse model of lupus (original) (raw)
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Do follicular dendritic cells regulate lupus-specific B cells?
Molecular Immunology, 2014
The factors that allow self-reactive B cells to escape negative selection and become activated remain poorly defined. In this review we describe recently published results in which a B cell receptor-knock-in mouse strain specific for nucleolar self-antigens was bred with mice deficient in complement C4 and discuss the implications for the lupus field. Absence of C4 leads to a breakdown in the elimination of autoreactive B cell clones at the transitional stage. This is characterized by a relative increase in their response to a range of stimuli, entrance into follicles and a greater propensity to form self-reactive germinal centers. In this review, a model is proposed in which, in the absence of complement C4, inappropriate clearance of apoptotic debris promotes chronic activation of myeloid cells and follicular dendritic cells, resulting in secretion of Type I interferon. This allows for the maturation and activation of self-reactive B cell clones leading to increased spontaneous formation of germinal centers and subsequent generation of autoantibodies.
Dendritic Cell and Macrophage-Mediated Tolerance in Lupus-Prone Mice
During infection, immune cells respond to polyclonal activators, like bacterial and viral antigens, through innate immune responses. Therefore, mechanisms to regulate the activation of autoreactive B cells during polyclonal activation are necessary to prevent autoimmunity. Previous studies into the mechanisms of B cell tolerance have focused on B cell Receptor (BCR)-mediated regulation of autoreactive or chronically antigen-experienced B cells. However, the regulation of chronically antigen-experienced B cells during polyclonal activation is less understood. We recently identified a novel mechanism of tolerance wherein DCs and MΦs repress Ig secretion by autoreactive B cells. Polyclonal activators through Toll-like Receptors (TLRs) induce DCs and MΦs to secrete soluble factors (IL-6, sCD40L, and TNFα) that differentially regulate naïve and chronically antigen-experienced B cells. IL-6, sCD40L, and TNFα selectively repress chronically stimulated autoreactive B cells while having no e...
Defective in Repressing Immunoglobulin Dendritic Cells from Lupus-Prone Mice Are
2007
Autoimmunity results from a breakdown in tolerance mechanisms that regulate autoreactive lymphocytes. We recently showed that during innate immune responses, secretion of IL-6 by dendritic cells (DCs) maintained autoreactive B cells in an unresponsive state. In this study, we describe that TLR4-activated DCs from lupus-prone mice are defective in repressing autoantibody secretion, coincident with diminished IL-6 secretion. Reduced secretion of IL-6 by MRL/lpr DCs reflected diminished synthesis and failure to sustain IL-6 mRNA production. This occurred coincident with lack of NF-B and AP-1 DNA binding and failure to sustain IB␣ phosphorylation. Analysis of individual mice showed that some animals partially repressed Ig secretion despite reduced levels of IL-6. This suggests that in addition to IL-6, DCs secrete other soluble factor(s) that regulate autoreactive B cells. Collectively, the data show that MRL/lpr mice are defective in DC/IL-6-mediated tolerance, but that some individuals maintain the ability to repress autoantibody secretion by an alternative mechanism.
Immunologic Research
Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by increased autoantibody production that leads to multiple tissue injuries. Dendritic cells (DCs) are important orchestrators of immune responses and key components in fine-tuning the balance between tolerance and immunity. However, their role in autoimmune disorders such as SLE remains uncertain. We analyzed the contribution of DCs in triggering SLE by adoptively transferring splenic DCs from aged autoimmune [NZB×NZW]F1 (BWF1) mice to young healthy BWF1 mice. We observed that the transfer of DCs from autoimmune mice to pre-autoimmune mice induced high autoantibody titers in the serum of recipient mice. Moreover, autoimmune DCs from aged BWF1 mice were crucial for the expansion and differentiation of plasmablasts and CD5 + B cells or B1-like cells in the peripheral blood, and spleen of recipient BWF1 mice, a phenomenon that is observed in autoimmune BWF1 mice. On the other hand, DCs from aged BWF1 mice participated in the expansion and differentiation of DCs and IFN-γ-producing T cells. These results reveal that DCs from autoimmune BWF1 mice exhibit functional and phenotypic characteristics that allow them to trigger B cell hyperactivation, as well as DC and T cell expansion and differentiation, thereby promoting an exacerbated humoral response in lupus-prone mice.
B lymphocytes enhance interferon-α production by plasmacytoid dendritic cells
Arthritis & Rheumatism, 2012
The type I interferon (IFN) system and B cells are activated in many autoimmune diseases, such as systemic lupus erythematosus (SLE). The IFN␣ produced by plasmacytoid dendritic cells (PDCs) stimulates several B cell functions, including autoantibody production. However, not much is known about how B cells influence PDC function. The aim of this study was to investigate the regulatory effect of B cells on IFN␣ production by PDCs. Methods. PDCs and B cells isolated from peripheral blood mononuclear cells from healthy blood donors were stimulated with RNA-containing immune complexes (ICs) consisting of U1 small nuclear RNP and SLE IgG, herpes simplex virus, or oligonucleotide (ODN) 2216, alone or in cocultures. IFN␣, several other cytokines, and PDC-or B cell-associated surface molecules were analyzed using immunoassays or flow cytometry. Results. B cells enhanced IFN␣ production by PDCs up to 47-fold, and the effect was most pronounced for PDCs stimulated with RNA-containing ICs. Anti-CD31 antibody reduced RNA-containing IC-induced IFN␣ production by 80% but had no effect on IFN␣ production when ODN 2216 was used as an inducer. Supernatants from ODN 2216-stimulated B cells promoted IFN␣ production by PDCs, while supernatants from RNA-containing IC-stimulated B cells did not. Conclusion. Our results showed that a novel function of B cells is enhancement of type I IFN production by PDCs. Because B cells are activated by type I IFN, this PDC-B cell cross-talk might be of fundamental importance in the etiopathogenesis of SLE and contribute to long-term immune activation in SLE and other systemic rheumatic diseases.
Laboratory Investigation, 2008
Marginal zone (MZ) B cells contain a large number of autoreactive clones and the expansion of this compartment has been associated with autoimmunity. MZ B cells also efficiently transport blood-borne antigen to the follicles where they activate T cells and differentiate into plasma cells. Using the B6.NZM2410.Sle1.Sle2.Sle3 (B6.TC) model of lupus, we show that the IgM+ CD1d(hi)/MZ B-cell compartment is expanded, and a large number of them reside inside the follicles. Contrary to the peripheral B-cell subset distribution and their activation status, the intrafollicular location of B6.TC IgM+ CD1d(hi)/MZ B cells depends on both bone marrow- and stromal-derived factors. Among the factors responsible for this intrafollicular location, we have identified an increased response to CXCL13 by B6.TC MZ B cells and a decreased expression of VCAM-1 on stromal cells in the B6.TC MZ. However, the reduced number of MZ macrophages observed in B6.TC MZs was independent of the IgM+ CD1d(hi)/B-cell location. B7-2 but not B7-1 deficiency restored IgM+ CD1d(hi)/MZ B-cell follicular exclusion in B6.TC mice, and it correlated with tolerance to dsDNA and a significant reduction of autoimmune pathology. These results suggest that follicular exclusion of IgM+ CD1d(hi)/MZ B cells is an important B-cell tolerance mechanism, and that B7-2 signaling is involved in breaching this tolerance checkpoint.
The regulation of autoreactive B cells during innate immune responses
Immunologic Research, 2008
Systemic lupus erythematosus (SLE) highlights the dangers of dysregulated B cells and the importance of initiating and maintaining tolerance. In addition to central deletion, receptor editing, peripheral deletion, receptor revision, anergy, and indifference, we have described a new mechanism of B cell tolerance wherein dendritic cells (DCs) and macrophages (MUs) regulate autoreactive B cells during innate immune responses. In part, DCs and MUs repress autoreactive B cells by releasing IL-6 and soluble CD40L (sCD40L). This mechanism is selective in that IL-6 and sCD40L do not affect Ig secretion by naïve cells during innate immune responses, allowing immunity in the absence of autoimmunity. In lupus-prone mice, DCs and MUs are defective in secretion of IL-6 and sCD40L and cannot effectively repress autoantibody secretion suggesting that defects in DC/MUmediated tolerance may contribute to the autoimmune phenotype. Further, these studies suggest that reconstituting DCs and MUs in SLE patients might restore regulation of autoreactive B cells and provide an alternative to immunosuppressive therapies.
F1000 - Post-publication peer review of the biomedical literature, 2000
Dendritic cells (DCs) initiate and control the adaptive immune response against infections. However, their contributions to the anti-self adaptive immune response in autoimmune disorders like systemic lupus erythematosus are uncertain. By constitutively deleting DCs in MRL.Fas lpr mice we show that they have complex roles in murine lupus. The net effect of DC deletion was to ameliorate disease. DCs were crucial for the expansion and differentiation of T cells but, surprisingly, not required for their initial activation. Correspondingly, kidney interstitial infiltrates developed in the absence of DCs, but failed to progress. DC deletion concomitantly decreased inflammatory and regulatory T cell numbers. Unexpectedly, plasmablast numbers and autoantibody concentrations depended on DCs, in contrast to total serum immunoglobulin concentrations, suggesting an effect of DCs on extrafollicular humoral responses. These findings reveal that DCs operate in unanticipated ways in murine lupus and validate them as a potential therapeutic target in autoimmunity.
The Journal of Immunology, 2008
Polyclonal B cell activation is a well-described feature of systemic lupus erythematosus (SLE), but the immune mechanisms leading to this activation are unclear. To gain insight into these processes, we extensively characterized the activated peripheral blood B cell populations in SLE. PBMC from lupus patients and healthy controls were stained with various combinations of conjugated Ab to identify distinct peripheral B cell subsets, and activation was assessed by measurement of forward scatter and CD80 or CD86 expression using flow cytometry. SLE patients had altered proportions of several B cell subsets, many of which demonstrated increased activation as assessed by forward scatter. This activation occurred at an early developmental stage, as B cells in the transitional (T2) stage were already significantly larger than those seen in controls. Increased proportions of CD80-or CD86expressing cells were also seen in multiple B cell subsets, with the most striking differences observed in the naive CD27 ؊ CD23 ؉ population. Within the CD23 ؉ subset, increased costimulatory molecule expression was most pronounced in an IgD ؉ IgM low population, suggesting that activation follows Ag engagement. Although controls also had IgD ؉ IgM low CD23 ؉ cells, they were reduced in number and not activated. Thus, there is an altered response to Ig receptor engagement with self-Ags in lupus.