Experimental lupus nephritis in severe combined immunodeficient (SCID) mice: remodelling of the glomerular lesions by bystander IgM antibodies

The CCL2-CCR2 axis determines whether glomerular endocapillary hypercellularity or wire-loop lesions develop through glomerular macrophage and neutrophil infiltration in lupus nephritis

The CCL2-CCR2 axis is involved in lupus nephritis, however the precise roles in the mechanisms by which different pathological lesions develop after glomerular immune complex deposition remain elusive. Previously, we demonstrated that genetic CCR2 inhibition induced a histological switch from glomerular endocapillary hypercellularity to wire-loop lesions in murine lupus nephritis. This study aimed to clarify the CCL2-CCR2 axis-mediated cellular mechanism in the formation of these different pathological lesions. We injected MRL/lpr mouse-derived monoclonal IgG3 antibody-producing hybridomas, 2B11.3 or B1, into wild-type (WT) mice to selectively induce glomerular endocapillary hypercellularity or wire-loop lesions. The expression of chemokine and chemokine receptors was analyzed using RT-quantitative PCR and/or immunofluorescence. We found 2B11.3 caused glomerular endocapillary hypercellularity in WT mice with glomerular infiltration of larger numbers of CCR2-expressing macrophages and neutrophils phagocyting immune complex, whereas B1 induced wire-loop lesions. In glomerular endocapillary hypercellularity, CCL2 was identified as the ligand involved in the CCR2-positive cell infiltration; it was expressed by glomerular endothelial cells and macrophages. Notably, 2B11.3-induced glomerular endocapillary hypercellularity converted to wire-loop lesions with reduced glomerular macrophage and neutrophil infiltration in CCL2-deficient (Ccl2-/-) mice similarly observed in Ccr2-/- mice. Moreover, this histological conversion was also observed when both glomerular macrophage and neutrophil infiltration were inhibited in anti-Ly6G antibody-treated Ccr5-/- mice but not when only glomerular macrophage infiltration was inhibited in Ccr5-/- mice or when only glomerular neutrophil infiltration was inhibited in anti-Ly6G antibody-treated WT mice. In contrast, B1 injection caused wire-loop lesions in Ccl2-/- and Ccr2-/- mice, as observed in WT mice. Moreover, 2B11.3 induced CCL2 from glomerular endothelial cells to a larger extent than B1 when injected into Ccr2-/- mice. In conclusion, the CCL2-CCR2 axis determines whether glomerular endocapillary hypercellularity or wire-loop lesions develop by regulating glomerular infiltration of phagocytic cells: macrophages and neutrophils. © 2024 The Pathological Society of Great Britain and Ireland.

Bortezomib treatment induces a higher mortality rate in lupus model mice with a higher disease activity

Background

Bortezomib (Bz) is a proteasome inhibitor that directly targets antibody-producing plasma cells. We recently reported the first randomized control trial that evaluated the effects of Bz in patients with systemic lupus erythematosus (SLE). In that study, we demonstrated that Bz treatment is associated with many adverse reactions in patients with refractory disease. In the present study, we examine the therapeutic and toxic effects of Bz on MRL/MpJ-lpr/lpr (MRL/lpr) mice with severe disease activity.

Methods

Female MRL/lpr mice at 10 and 14 weeks of age were treated with phosphate buffered saline (PBS) (n = 19), Bz (750 μg/kg twice weekly) (n = 27), or cyclophosphamide (Cyc) (1 mg/body, once in 2 weeks) (n = 20). Cellular subsets, serum immunoglobulin, anti-double-stranded DNA (anti-dsDNA) antibody titer, and a pathological index of glomerulonephritis were then analyzed at 22 weeks of age. Survival curves of the 10-week-old and 14-week-old Bz-treated groups were compared. Blood counts, creatinine, liver enzymes, and serum cytokine levels were measured 1 week after Bz treatment. Gene expression profiling of spleens from Bz and Cyc treatment mice were compared with those from control mice.

Results

The anti-dsDNA antibody levels were significantly higher in 14-week-old than in 10-week-old mice, indicating a higher disease activity at 14 weeks. A significant decrease in the number of splenic cells and glomerulonephritis index was observed in Bz-treated and Cyc-treated mice. Bz, but not Cyc, significantly decreased serum immunoglobulin and anti-dsDNA antibody titer levels. Survival curve analysis revealed a significantly higher mortality rate in 14-week-old than in 10-week-old Bz-treated and control groups. Following two injections of Bz, serum IL-6 and TNF-α levels were significantly more elevated in 14-week-old than in 10-week-old mice. Potentially immunogenic molecules, such as heat shock proteins, were characteristically upregulated in spleens of Bz-treated but not Cyc-treated mice.

Conclusions

In spite of its therapeutic effect, Bz treatment had more toxic effects associated with increased proinflammatory cytokine levels in mice with a higher disease activity. Understanding the mechanism of the toxicity and developing preventive strategies against it is important for the safe clinical application of Bz in human SLE.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-017-1397-7) contains supplementary material, which is available to authorized users.

Association between E-selectin expression and histopathological modification of glomerular lesions by non-nephritogenic IgM antibodies in experimental lupus nephritis

OBJECTIVE

To examine the role played by E-selectin in bystander IgM-mediated modification of glomerular lesions in experimental lupus nephritis.

METHODS

Experimental lupus SCID mice were induced by an intraperitoneal injection of clone 7B6.8, which was derived from a MRL/lpr mouse and shown to induce wire-loop type glomerular lesions. Mice were subsequently administered clone Sp6, a non-nephritogenic IgM antibody- producing hybridoma. E-selectin expression was then evaluated in glomeruli showing histopathological conversion of lesions from wire-loop-like to a cell-proliferative form. We also investigated the effects of a circulating soluble form of E-selectin (sE-selectin) on the modification of glomerular lesions in this lupus model.

RESULTS

In experimental lupus mice, glomerular E-selectin expression significantly increased during the conversion from wire-loop-like glomerular lesions to a cell-proliferative type mediated by a non-nephritogenic bystander IgM antibody in presence of a nephritogenic antibody. Intraglomerular infiltration of CD68 + macrophages correlated significantly with the glomerular level of E-selectin expression. In addition, overexpression of circulating sE-selectin significantly suppressed conversion to cell-proliferative glomerular lesions and glomerular macrophage infiltration in these lupus model mice.

CONCLUSIONS

The histopathological modification of lupus nephritis by non-nephritogenic bystander IgM antibodies is associated in part with glomerular E-selectin expression.

Sugar-free, glycine-stabilized intravenous immunoglobulin prevents skin but not renal disease in the MRL/lpr mouse model of systemic lupus

Intravenous immunoglobulin (IVIG) has a therapeutic potential in many autoimmune diseases. Based on its immune modulating and complement inhibiting effects, IVIG has been tested in systemic lupus erythematosus (SLE), but due to osmotic tubular injury caused by immunoglobulin-stabilizing sugar components, lupus nephritis had been accelerated in some patients, thus IVIG use in SLE has been abandoned. The availability of non-sugar-stabilized IVIG raised the possible re-evaluation of IVIG for SLE. We investigated high-dose, long-term non-sugar-stabilized IVIG treatment on skin and renal SLE manifestations in the MRL/lpr mouse model. Animals were treated once a week with glycine-stabilized IVIG or saline (0.2 ml/ 10 g BW) from 6 weeks until they were humanely killed at 5 months of age. IVIG diminished macroscopic cutaneous lupus compared with saline treated mice. Histology and complement-3 immunostaining also demonstrated a significant reduction of skin disease after IVIG treatment. However, renal histology and function were similar in both groups. Compared with typical osmotic tubular damage induced by 5% sucrose and 10% maltose (used for IVIG stabilization), we did not observe any osmotic tubular injury in the glycine-stabilized IVIG treated mice. Our data demonstrate a beneficial effect of IVIG on skin lupus without renal side-effects. Deeper understanding of the organ-specific pathomechanism may aid an individualized SLE therapy.

Deficiency in activation-induced cytidine deaminase promotes systemic autoimmunity in lpr mice on a C57BL/6 background

Activation-induced deaminase (AID) is a prerequisite for immunoglobulin (Ig) class-switch recombination and somatic hypermutation, which is critical for antibody affinity maturation. IgM and IgG autoantibodies are characteristic of the systemic autoimmune disorders such as lupus. However, the relative contributions of hypermutated high-affinity IgG antibodies and germline-encoded IgM antibodies to systemic autoimmunity are not defined fully. The role of AID in autoimmunity is unclear. The current study used AID-deficient mice to investigate the role of AID in the development and pathogenesis of murine lupus. C57BL/6 mice deficient in both Fas and AID were generated. Compared to their AID-competent littermates, AID(-/-) lymphoproliferative (lpr) mice produced significantly elevated levels of IgM autoreactive antibodies with enhanced germinal centre (GC) response, developed more advanced splenomegaly and exhibited more severe glomerulonephritis. Thus, AID may play an important role in the negative regulation of systemic autoimmune manifestations in murine lupus. The results also indicate that hypermutated high-affinity IgG antibodies are not necessary for the development of autoimmune syndrome in lpr mice on a C57BL/6 background.

Abrogation of lupus nephritis in activation-induced deaminase-deficient MRL/lpr mice

We generated MRL/lpr mice deficient in activation-induced deaminase (AID). Because AID is required for Ig hypermutation and class switch recombination, these mice lack hypermutated IgG Abs. Unlike their AID wild-type littermates, AID-deficient MRL/lpr mice not only lacked autoreactive IgG Abs but also experienced a dramatic increase in the levels of autoreactive IgM. This phenotype in AID-deficient mice translated into a significant reduction in glomerulonephritis, minimal mononuclear cell infiltration in the kidney, and a dramatic increase in survival to levels comparable to those previously reported for MRL/lpr mice completely lacking B cells and well below those of mice lacking secreted Abs. Therefore, this study wherein littermates with either high levels of autoreactive IgM or autoreactive IgG were directly examined proves that autoreactive IgM Abs alone are not sufficient to promote kidney disease in MRL/lpr mice. In addition, the substantial decrease in mortality combined with a dramatic increase in autoreactive IgM Abs in AID-deficient MRL/lpr mice suggest that autoreactive IgM Abs might not only fail to promote nephritis but may also provide a protective role in MRL/lpr mice. This novel mouse model containing high levels of autoreactive, unmutated IgM Abs will help delineate the contribution of autoreactive IgM to autoimmunity.

Biosensor analysis of beta2-glycoprotein I-reactive autoantibodies: evidence for isotype-specific binding and differentiation of pathogenic from infection-induced antibodies

BACKGROUND

For the laboratory diagnosis of the antiphospholipid syndrome (APS) we developed a biosensor with the ability to distinguish between disease-relevant anti-beta2-glycoprotein I (beta2GPI) autoantibodies (anti-beta2GPI) and pathogen-specific beta2GPI cross-reactive antibodies that occur transiently during infections.

METHODS

We used a surface plasmon resonance (SPR) biosensor device. For the detection of anti-beta2GPI in serum samples, affinity-purified human beta2GPI was covalently attached to a functionalized n-alkanethiol self-assembling monolayer on the biosensor chip. After verifying the specificity of the biosensor system with a panel of monoclonal antibodies to beta2GPI, we analyzed sera from healthy donors and patients suffering from APS, systemic lupus erythematosus (SLE), syphilis, or parvovirus B19 infections. The SPR results were compared with beta2GPI-specific ELISA.

RESULTS

Using the SPR biosensor, we recorded antigen binding curves with response levels in the range of 50-500, resonance units (RU) for anti-beta2GPI ELISA-positive APS patient sera. The amplitudes of the antiphospholipid antibody (APL) responses in the biosensor correlated with the overall IgG and IgM anti-beta2GPI ELISA titers with a correlation coefficient of 0.87. Moreover, we observed immunoglobulin isotype-specific association and dissociation profiles for APL binding of different APS patient sera to the biosensor-immobilized beta2GPI. In contrast to APS patient samples, no significant anti-beta2GPI binding (response levels <35 RU) was observed in samples from healthy individuals or from patients suffering from SLE, syphilis, or parvovirus B19 infection.

CONCLUSIONS

The SPR biosensor system enables specific detection of APS-associated beta2GPI-reactive APL and differentiation from beta2GPI cross-reactive antibodies that occur frequently during acute infections. The established association/dissociation plot for anti-beta2GPI responses in APS patient sera gives additional information regarding the influence of anti-beta2GPI IgG and IgM isotype distribution.

Natural serum IgM maintains immunological homeostasis and prevents autoimmunity

Natural (i.e. low-affinity, preimmune) IgM has a wide range of actions in the immune system. That IgM is important in defence against infection has been recognised for many years but recently, due to the generation of mouse models specifically deficient in serum IgM, other functions of serum IgM have been revealed. The participation of natural IgM in autoimmunity has been a subject of speculation for some time, but there is recent definitive evidence that demonstrates its protective role. This review focuses on these new areas of research, which also show that many pathologies not normally recognised as having an immunological basis are modulated by serum IgM.

A human anti-dsDNA monoclonal antibody caused hyaline thrombi formation in kidneys of 'leaky' SCID mice

There are few studies assessing the pathogenicity of human monoclonal anti-DNA antibodies. The use of SCID mice avoids the problem of rejection of the human hybridoma cells thus allowing in vivo assessment of human immunoglobulins. Using electron microscopy we have shown that the human IgG anti-dsDNA monoclonal antibody, RH14, is nephritogenic in SCID mice, causing morphological changes in the kidney due to immunoglobulin deposition. The problem with using SCID mice is that they have an abnormal immune system; normally they are used at about 2 months of age, at which time they have virtually no functional T or B cells. It is known that older SCID mice become increasingly 'leaky', that is they develop some mature lymphocyte clones. Our aim was to assess if implanting anti-DNA antibodies into older 'leaky' SCID mice would result in pathology which was observable by light microscopy. Eight-month-old SCID mice were implanted with human hybridoma cells secreting either RH14 an anti-dsDNA IgG, CL24, an antiphospholipid antibody or an irrelevant human IgG control. As previously, RH14 deposited in the kidney and caused proteinuria but unexpectedly we also observed hyaline thrombi in the kidney glomeruli and peritubular capillaries. These thrombi occurred only in the case of RH14 implanted mice and were found to stain positively for human IgG and fibrin. However, apart from the interesting thrombi, we did not observe any greater pathological damage resulting from the anti-dsDNA antibody deposition than we had seen in the younger mice; indeed, the electron microscopic findings were more limited.

Renal immunofluorescence and the prediction of renal outcome in patients with proliferative lupus nephritis

The risk for endstage renal failure in patients with proliferative lupus nephritis (PLN) depends largely on the severity and reversibility of the inflammatory process as determined by light microscopy (LM). As the intrarenal formation of immune complexes is thought to initiate this inflammation, we studied whether renal immunofluorescence microscopy (IFM) provides clinical or prognostic information in addition to LM findings. Clinical data at the time of renal biopsy and during a mean follow-up of 46 months were extracted from the records of 69 SLE patients with proliferative LN (WHO class III/IV). Biopsy specimens were analyzed by LM for AI and CI, while IFM was performed on cryostat sections with the use of antisera against IgG, IgM, IgA, C3, C1q and fibrin. IFM findings were recorded in terms of the localization (glomerular, tubular or vascular) and intensity of fluorescence (score from zero to three). IFM findings were then related to clinical and LM findings and its prognostic value studied by survival analysis. Glomerular immune deposits were present in 99% of patients, tubular deposits in 38% and vascular deposits in 17%. A 'full-house' pattern (all three Ig classes) was found in 67% of biopsies and C3 and C1q deposits in 93% and 74% respectively. Median scores for AI and CI were 6 (1-18) and 3 (0-10); aside from a negative correlation between IgA deposits and CI, we found no other correlation between the amount or type of immune deposits and AI or CI. IgM deposits were associated with high serum levels of anti-dsDNA, while IgG deposits correlated with high ESR and serum creatinin levels. IFM scores were not related to steroid dose at the time of biopsy and neither type of glomerular, tubular or overall renal immune deposits had prognostic value for renal survival. Renal immunofluorescence does not reflect light microscopy findings in patients with PLN and does not contribute prognostic information in patients with PLN. Lupus (2000) 9, 504-510.