In vitro and in vivo functional analysis of CD5+ and CD5- B cells of autoimmune NZB x NZW F1 mice

Dissociation of the genetic loci leading to b1a and NKT cell expansions from autoantibody production and renal disease in B6 mice with an introgressed New Zealand Black chromosome 4 interval

Previous mapping studies have linked New Zealand Black (NZB) chromosome 4 to several lupus traits, including autoantibody production, splenomegaly, and glomerulonephritis. To confirm the presence of these traits, our laboratory introgressed homozygous NZB chromosome 4 intervals extending from either 114 to 149 Mb or 32 to 149 Mb onto the lupus-resistant C57BL/6 background (denoted B6.NZBc4S and B6.NZBc4L, respectively). Characterization of aged cohorts revealed that B6.NZBc4L mice exhibited a striking increase in splenic B1a and NKT cells in the absence of high titer autoantibody production and significant renal disease. Tissue-specific expansion of these subsets was also seen in the peritoneum and liver for B1a cells and in the bone marrow for NKT cells. Staining with CD1d tetramers loaded with an alpha-galactosylceramide analog (PBS57) demonstrated that the expanded NKT cell population was mainly CD1d-dependent NKT cells. The lack of both cellular phenotypes in B6.NZBc4S mice demonstrates that the genetic polymorphism(s) that result in these phenotypes are on the proximal region of NZB chromosome 4. This study confirms the presence of a locus that promotes the expansion of B1a cells and newly identifies a region that promotes CD1d-restricted NKT cell expansion on NZB chromosome 4. Taken together, the data indicate that neither an expansion of B1a cells and/nor NKT cells is sufficient to promote autoantibody production and ultimately, renal disease.

Treatment with rituximab affects both the cellular and the humoral arm of the immune system in patients with SLE

Herein we investigated how rituximab-induced B cell depletion affected leukocyte subpopulations and antibody titers in SLE patients. We focused our analysis on time points related to absence and return of B cells after depletion. A correlation was found between the baseline frequency and time to repopulation; the fewer B cells initially, the longer to their return. While the few B cells remaining after treatment were of memory, double-negative (IgD-CD27-), and CD5+ phenotype, the returning B cells were mainly naïve, indicating de novo production of B cells. Serum levels of IgG and antibodies against Ro52, Ro60, La44, measles and tetanus remained unchanged, while decreases in IgM, IgE, anti-dsDNA and anti-C1q antibodies were observed. Additionally, a significant increase in activated CD4+ and CD8+ T cells, as well as CD25bright FOXP3+ regulatory T cells was observed. In conclusion, both the humoral and the cellular immune systems were affected by treatment with rituximab.

Analysis of RAG expression by peripheral blood CD5+ and CD5- B cells of patients with childhood systemic lupus erythematosus

BACKGROUND

The assembly of immunoglobulin genes during B cell development in the bone marrow is dependent on the expression of recombination activating genes (RAG) 1 and 2. Recently, RAG expression in peripheral blood IgD+ B cells outside the bone marrow has been demonstrated and is associated with the development of autoimmune diseases.

OBJECTIVE

To investigate RAG expression in the CD5+ or CD5- IgD+ B cell compartment in childhood systemic lupus erythematosus (SLE).

METHODS

Using a combination of flow cytometric cell sorting and reverse transcriptase polymerase chain reaction analysis of cDNA libraries generated from individual cells, the expression of RAG, VpreB, and CD154 mRNA by individual peripheral blood B cells of three paediatric SLE patients was examined in detail.

RESULTS

While only one patient had a significantly increased frequency of RAG+ B cells in the CD5- B cell population, all patients showed higher frequencies of RAG+ B cells in the CD5+IgD+ B cell population. The frequency of RAG+ IgD+CD5+/- B cells was reduced during intravenous cyclophosphamide treatment. In healthy age matched children, RAG expressing IgD+ B cells were hardly detectable. Coexpression of RAG and VpreB or CD154 mRNA could only be found in SLE B cells.

CONCLUSIONS

RAG expression in peripheral blood B cells of SLE patients is particularly increased in the IgD+CD5+ B cell population. CD5+ and CD5- B cells in SLE have the potential to undergo receptor revision leading to the generation of high affinity pathogenic autoantibodies.

Role of the chemokine stromal cell-derived factor 1 in autoantibody production and nephritis in murine lupus

In normal mice, stromal cell-derived factor 1 (SDF-1/CXCL12) promotes the migration, proliferation, and survival of peritoneal B1a (PerB1a) lymphocytes. Because these cells express a self-reactive repertoire and are expanded in New Zealand Black/New Zealand White (NZB/W) mice, we tested their response to SDF-1 in such mice. PerB1a lymphocytes from NZB/W mice were exceedingly sensitive to SDF-1. This greater sensitivity was due to the NZB genetic background, it was not observed for other B lymphocyte subpopulations, and it was modulated by IL-10. SDF-1 was produced constitutively in the peritoneal cavity and in the spleen. It was also produced by podocytes in the glomeruli of NZB/W mice with nephritis. The administration of antagonists of either SDF-1 or IL-10 early in life prevented the development of autoantibodies, nephritis, and death in NZB/W mice. Initiation of anti-SDF-1 mAb treatment later in life, in mice with established nephritis, inhibited autoantibody production, abolished proteinuria and Ig deposition, and reversed morphological changes in the kidneys. This treatment also counteracted B1a lymphocyte expansion and T lymphocyte activation. Therefore, PerB1a lymphocytes are abnormally sensitive to the combined action of SDF-1 and IL-10 in NZB/W mice, and SDF-1 is key in the development of autoimmunity in this murine model of lupus.

Origins and functions of B-1 cells with notes on the role of CD5

Whether B-1a (CD5+) cells are a distinct lineage derived from committed fetal/neonatal precursors or arise from follicular B-2 cells in response to BCR ligation and other, unknown signals remains controversial. Recent evidence indicates that B-1a cells can derive from adult precursors expressing an appropriate specificity when the (self-) antigen is present. Antibody specificity determines whether a B cell expressing immunoglobulin transgenes has a B-2, B-1a or marginal zone (MZ) phenotype. MZ cells share many phenotypic characteristics of B-1 cells and, like them, appear to develop in response to T independent type 2 antigens. Because fetal-derived B cell progenitors fail to express terminal deoxynucleotidyl transferase (TdT) and for other reasons, they are likely to express a repertoire that allows selection into the B-1a population. As it is selected by self-antigen, the B-1 repertoire tends to be autoreactive. This potentially dangerous repertoire is also useful, as B-1 cells are essential for resistance to several pathogens and they play an important role in mucosal immunity. The CD5 molecule can function as a negative regulator of BCR signaling that may help prevent inappropriate activation of autoreactive B-1a cells.

The effect of cytokines on the activation-induced apoptosis of B cells in autoimmune NZB x NZW F1 mice

Programmed cell death (apoptosis) is an essential process in the development of various tissues and its involvement has been proposed for the elimination of self-reactive immature T and B lymphocytes when self antigens are first encountered. In order to further investigate the role of apoptosis in the pathogenesis of autoimmune disease, the apoptosis of lipopolysaccharide (LPS)-activated B cells, peritoneal cells from NZB x NZW F1 (NZB/W F1) mice and nonautoimmune BALB/c mice were assayed using an in vitro culture system. Splenic B cells were isolated and then stimulated with LPS before further activated with crosslinking antimu antibody. In addition, the apoptosis of peritoneal cells induced by crosslinking antimu antibody was also analyzed. The data revealed that the specific apoptosis of both activated B cells and peritoneal cells induced by crosslinking antimu antibody was very similar comparing NZB/W F1 and nonautoimmune BALB/c mice. This activation-induced B-cells apoptosis could be rescued, however, with the addition of cytokines such as interleukin (IL)-5 or IL-10, to the culture. The results suggest that there is no endogenous defect in the apoptosis of activated B cells for autoimmune NZB/W F1 comparing nonautoimmune BALB/c mice. Notably, however, abnormally high levels of the type 2 T helper (Th2)-related cytokines such as IL-5 or IL-10 may play an important role in the abnormal expansion of activated B cells in autoimmune NZB/W F1 mice.

Dietary conjugated linoleic acid protects against end stage disease of systemic lupus erythematosus in the NZB/W F1 mouse

Conjugated linoleic acid (CLA) is a naturally occurring fatty acid with anti-carcinogenic, anti-atherosclerotic and immune-enhancing activities. Dietary CLA accelerated the onset of proteinuria in autoimmune-prone NZB/W F1 mice but did not affect anti-DNA antibody production. Body weight of the CLA group was decreased compared to the control group at the time proteinuria first developed. CLA group also had slightly earlier mortality than control fed mice, however the mean days of survival did not differ between CLA and control fed mice. Body weight loss between proteinuria onset and death was approximately twice as much in the control group as in the CLA group. Moreover, duration between proteinuria and death was longer in the CLA than in the control group. Our data suggested that dietary CLA may accelerate the autoimmune symptoms of NZB/W F1 mice, however, CLA protected against the disease related body weight loss and prolonged survival after proteinuria.

Tamoxifen alleviates disease severity and decreases double negative T cells in autoimmune MRL-lpr/lpr mice

Previous study suggested that MRL-lpr/lpr mice treated with tamoxifen (TAM) had less severe proteinuria, reduced serum titre of anti-dsDNA autoantibodies and an increased survival rate. To investigate further the regulatory mechanisms of TAM on MRL-lpr/lpr female mice, a total dose of 200 microg per mice (5.5 mg/kg) was given every 2 weeks subcutaneously, while the control mice were injected with oil only. After being treated with TAM four times, the mice were killed and cellular functions were evaluated. The TAM-treated groups had smaller sized spleen and lymph nodes. Flow cytometric analysis of splenocytes had a significantly lower percentage of cell number of T cells and double negative T cells (CD4- CD8- T cells). There was no difference in cytokine production (interleukin (IL)-2, IL-4, IL-5, IL-10 and interferon-gamma (IFN-gamma)) from splenocytes stimulated with concanavalin A (Con A) or cytokines (IL-6) secreted by peritoneal exudate cells when stimulated with lipopolysaccharide (LPS). However, IL-2 from lymph node cells was significantly higher on TAM-treated mice. Finally, splenocytes or purified T cells stimulated with anti-CD3 antibody plus cross-linking immunoglobulin G (IgG) of the TAM-treated group had higher 3H-incorporation of proliferation assay compared with that of control groups. In vitro study further demonstrated that IL-2-activated proliferation of lymph node double negative (DN) T cells can be inhibited by TAM treatment in a dose-dependent manner. Our finding demonstrated that TAM may potentially influence T cells and modulate the immune function, which offers a novel approach to explore the feasibility of hormone therapy for autoimmune diseases.

Ganglioside GQ1b enhances anti-double-stranded DNA antibody and IgG production of PBMCs from patients with systemic lupus erythematosus

BACKGROUND

Previously, we reported that ganglioside GQ1b greatly enhanced spontaneous immunoglobulin production in vitro by PBMCs from normal human subjects.

OBJECTIVE

We examined in vitro effects of GQ1b on anti-double-stranded DNA (anti-dsDNA) antibody production by PBMCs from patients with systemic lupus erythematosus (SLE).

METHODS

PBMCs from patients with SLE were cultured with GQ1b. IgG anti-dsDNA antibody, total IgG, and cytokine amounts in the culture supernatants and protein kinase C (PKC) activity of T cells were measured by using ELISA.

RESULTS

GQ1b enhanced both anti-dsDNA and total IgG production of PBMCs from patients with SLE who were seropositive for anti-dsDNA. Among the seropositive patients, the active patients were more responsive to GQ1b in anti-dsDNA production than the inactive patients. GQ1b also enhanced total IgG production of PBMCs from patients with SLE who were seronegative for anti-dsDNA but did not induce their anti-dsDNA production. In contrast to PBMCs, GQ1b did not affect the antibody production either of purified CD5(+) or of CD5(-) B cells. Anti-IL-6 or anti-IL-10 antibody each partially blocked the GQ1b-induced enhancement of antibody production in PBMCs, and the addition of both antibodies completely blocked the enhancement. GQ1b increased IL-6 and IL-10 production of T cells. The supernatant from GQ1b-treated T cells enhanced antibody production both of CD5(+) and of CD5(-) B cells to a greater extent than that from medium-treated T cells. Exogenous IL-6 and IL-10 additively increased the antibody production both of CD5(+) and CD5(-) B cells. GQ1b-induced increases in IL-6 and IL-10 production of T cells were both blocked by PKC inhibitors, calphostin C and staurosporine. GQ1b enhanced PKC activity of T cells.

CONCLUSION

These results suggest that GQ1b may polyclonally increase the production of IgG, including IgG anti-dsDNA antibody, in PBMCs from patients with SLE by promoting IL-6 and IL-10 production of T cells through the enhancement of their PKC activity.

Accumulation of splenic B1a cells with potent antigen-presenting capability in NZM2410 lupus-prone mice

OBJECTIVE

In order to shed light on the role of splenic B1 cells in disease pathogenesis in lupus-prone mice, this study was undertaken to determine how efficiently these cells can serve as antigen-presenting cells (APC) and to ascertain which murine lupus susceptibility loci dictate the expansion of these cells.

METHODS

Spleens and peritoneal cavities (PerC) of NZM2410 lupus-prone mice, as well as of control B6 and New Zealand white mice, were examined for the prevalence, surface phenotype, and possible anatomic location of B1 cells. The antigen-presenting ability of fluorescence-sorted splenic B1a cells was assessed. Levels of B1 cells were examined in B6 mice congenic for 4 different lupus susceptibility intervals.

RESULTS

NZM2410 lupus mice showed an expansion of splenic and PerC B1a cells at all ages. These cells expressed high levels of B71, B72, CD24, lymphocyte function-associated antigen 1, and intercellular adhesion molecule 1, and had the functional capability to serve as APC. Among the lupus susceptibility intervals studied, Sle2, but not Sle1, Sle3, or the H2 locus, affected the expansion of B1 cells.

CONCLUSION

These findings raise the possibility that the genetically determined expansion of splenic B1a cells in lupus-prone mice might contribute to disease pathogenesis by augmenting the presentation of autoantigens to pathogenic T cells.

Self-reactive antibodies (natural autoantibodies) in healthy individuals

Antibodies that are present in the serum of healthy individuals in the absence of deliberate immunization with any antigen, are refered to as natural antibodies. A vast majority of natural antibodies react with one or more self antigens and are termed as natural autoantibodies. The importance of natural autoantibodies in immune regulation has long been neglected, since tolerance to self was thought to be primarily dependent on the deletion of autoreactive clones, rather than on peripheral suppressive mechanisms. Clonal deletion and energy cannot account, however, for the prevalence of natural autoreactivity among healthy individuals. It is now well established that autoreactive antibodies and B cells, and autoreactive T cells, are present in healthy individuals, and in virtually all vertebrate species. Autoreactive repertoires are predominantly selected early in ontogeny. Questions pertaining to the role of natural antibodies in the regulation of the immune response and maintenance of immune homeostasis and to the distinction between natural autoreactivity and pathological autoimmunity have not been adequately addressed. Here, we focus on the current knowledge on the physicochemical and functional properties of NAA in man, and the use of NAA for therapeutic intervention. reserved.

Phenotypic and functional analysis of activated B cells of autoimmune NZB x NZW F1 mice

Polyclonal B-cell activation is the central theme in the production of autoantibodies and possible activation of autoreactive T cells in both human and murine lupus. The abnormal expansion of CD5+ B cells in murine lupus has been suggested, in particular, to be one of the most characteristic findings in these mice. Activated B cells can be separated from the B cells of resting stage by the difference in cell density. The aim of this study was to investigate the characteristics of different densities of the spleen cells separated by gradient density. Furthermore, the ability of anti-DNA antibody secretion in each percoll gradient fraction of B cells was also analysed. The results showed: a higher percentage of CD5+ B cells, which corresponded to the activated B-cell population, in percoll gradient 1 and 2 fractions; that splenic B cells of NZB/W F1 mice had proliferative response to interleukin (IL)-4 or IL-5 but not to IL-10 or interferon-gamma (IFN-gamma); and that B cells isolated by percoll gradient produced anti-DNA antibody after stimulation with lipopolysaccharide (LPS) plus IL-5 and IFN-gamma, but not IL-4 and IL-10. These data suggest that B cells at different stages of activation express differential characteristics and functions.