Umesh S. Deshmukh

Breaking Tolerance to Double Stranded DNA, Nucleosome, and Other Nuclear Antigens Is Not Required for the Pathogenesis of Lupus Glomerulonephritis

In lupus-prone NZM2328 mice, a locus Cgnz1 on chromosome 1 was linked to chronic glomerulonephritis, severe proteinuria, and early mortality in females. A locus Adnz1 on chromosome 4 was linked to antinuclear antibody (ANA) and anti–double stranded DNA (dsDNA) antibody (Ab) production. In this investigation, two congenic strains, NZM2328.C57L/Jc1 (NZM.C57Lc1) and NZM2328.C57L/Jc4 (NZM.C57Lc4), were generated by replacing the respective genetic intervals containing either Cgnz1 or Adnz1 with those from C57L/J, a nonlupus-prone strain. The NZM.C57Lc1 females had markedly reduced incidence of chronic glomerulonephritis and severe proteinuria. NZM.C57Lc4 females had chronic glomerulonephritis and severe proteinuria without circulating ANA, anti-dsDNA, and antinucleosome Ab. These data confirm the linkage analysis. Unexpectedly, NZM.C57Lc1 females had little anti-dsDNA and related Ab, suggesting the presence of a second locus Adnz2 on chromosome 1. The diseased NZM.C57Lc4 kidneys had immune complexes by immunofluorescence and electron microscopy. The eluates from these kidneys did not contain ANA, anti-dsDNA, and antinucleosome Ab, indicative of the presence of non–anti-dsDNA nephritogenic Ab. Thus, breaking tolerance to dsDNA and chromatin is not required for the pathogenesis of lupus nephritis. These results reaffirm that anti-dsDNA and related Ab production and chronic glomerulonephritis are under independent genetic control. These findings have significant implications in the pathogenesis of systemic lupus erythematosus.

Activation of innate immune responses through Toll-like receptor 3 causes a rapid loss of salivary gland function

BACKGROUND Recent studies have demonstrated the expression of Toll-like receptor 3 (TLR3) in salivary glands and epithelial cell lines derived from Sjögrens syndrome (SS) patients. As viral infections are considered to be a trigger for SS, in this study we investigated whether in vivo engagement of TLR3 affects salivary gland function. METHODS Female New Zealand Black/WF1 mice were repeatedly injected with polyinosinic:polycytidylic acid [poly(I:C)]. TLR3 expression within submandibular glands was studied using immunohistochemistry. RNA levels of inflammatory cytokines in the submandibular glands were determined by real time polymerase chain reaction. Pilocarpine induced saliva volume was used as an index of glandular function. RESULTS Immunohistochemical analysis of submandibular glands showed TLR3 expression in epithelium of serous and mucous acini, granular convoluted tubules, and ducts. Poly(I:C) treatment rapidly up-regulated the mRNA levels of type I interferon (IFN) and inflammatory cytokines in the submandibular glands. One week after treatment, the saliva volumes in poly(I:C) treated mice were significantly reduced in comparison with the phosphate-buffered saline (PBS) treated mice. Hematoxylin and eosin staining showed that salivary gland histology was normal and lymphocytic foci were not detected. Glandular function recovered after poly(I:C) treatment was stopped. CONCLUSIONS Our results demonstrate that engagement of TLR3 within the salivary glands results in a rapid loss of glandular function. This phenomenon is associated with the production of type I IFN and inflammatory cytokines in the salivary glands. Restoration of glandular function suggests that for viral etiology of SS, a chronic infection of salivary glands might be necessary.

Role for Nephritogenic T Cells in Lupus Glomerulonephritis: Progression to Renal Failure Is Accompanied by T Cell Activation and Expansion in Regional Lymph Nodes

Autoreactive T cells are critical in the initiation and maintenance of autoantibody responses that are a hallmark of systemic lupus erythematosus. However, the direct contribution of T cells in end-organ disease like lupus glomerulonephritis (GN) is poorly understood. In this study, we investigated the role of T cells in progression of lupus GN in NZM2328 mice, a murine model of spontaneous systemic lupus erythematosus. At 26 wk of age, NZM2328 female mice showed glomerular immune complex deposits and acute proliferative GN. This was associated with up-regulation of MHC class II and the detection of T cells and CD11c+ dendritic cells in the glomeruli. The regional lymph nodes (LN) showed preferential activation of T cells and an oligoclonal T cell response with skewed expansion of certain Vβ families. This suggests an Ag-driven response occurring in the regional LN of nephritic mice during acute GN. In contrast, male NZM2328 mice developed glomerular immune complexes and acute GN, but rarely progressed to fatal chronic GN. Significantly, male kidneys at 40 wk of age did not have detectable dendritic cells and T cells in the glomeruli. Thus, glomerular immune complex deposition initiates an immune response against renal Ags in the regional LN, leading to T cell recruitment into the kidney during acute proliferative GN. This T cell activation and infiltration are influenced by gender-dependent end-organ factors and may determine the progression of acute GN to chronic GN and renal failure.

HLA Class II Influences the Immune Response and Antibody Diversification to Ro60/Sjögren’s Syndrome-A: Heightened Antibody Responses and Epitope Spreading in Mice Expressing HLA-DR molecules

Abs to Ro/SSA Ags in the sera of patients with systemic lupus erythematosus and Sjögren’s syndrome are influenced by the HLA class II genes. To investigate the role of individual HLA class II genes in immune responses to human Ro60 (hRo60), mice lacking murine class II molecules and carrying either HLA genes DR2(DRB1*1502), DR3(DRB1*0301), DQ6(DQA1*0103/DQB1*0601), or DQ8(DQA1*0301/DQB1*0302), were immunized with rhRo60. The results show that hRo60 induces strong T and B cell responses in DR2, DR3, and DQ8 mice in comparison to weaker responses in DQ6 mice. In all mice, the majority of the dominant T cell epitopes were located in the amino portion (aa 61–185) and the carboxy portion (aa 381–525) of the hRo60 molecules. In contrast, the early dominant B cell epitopes were located in the middle and carboxy portion of the hRo60 molecule (aa 281–315 and 401–538). In DR2, DR3, and DQ8 mice, the B cell epitopes subsequently spread to the amino and carboxy portion of the hRo60 molecule but were limited to the middle and carboxy portion in DQ6 mice. The DR2 and DR3 mice produced the highest titers of immunoprecipitating Abs against hRo60 and native mouse Ro60. In addition, only DR2 mice exclusively produced immunoprecipitating Abs to native mouse Ro52 and Abs to mouse La by slot blot analysis, whereas in other strains of mice Abs to mouse La were cross-reactive with the immunogen. The results of the present study demonstrate the importance of HLA class II in controlling the immune responses to the Ro-ribonucleoprotein.

Ro60 peptides induce antibodies to similar epitopes shared among lupus-related autoantigens.

The coexistence of autoantibodies to ribonucleoproteins (RNP) in sera of patients with systemic lupus erythematosus has been attributed to intermolecular determinant spreading among physically associated proteins. Recently, we showed that murine Ab responses to rRo60 or Ro60 peptides were diversified unexpectedly to small nuclear RNP. In this investigation, the mechanisms for this autoantibody diversification were examined. Intramolecular determinant spreading was demonstrated in mice immunized with human or mouse Ro60316–335. Immune sera depleted of anti-peptide Ab immunoprecipitated Ro60-associated mY1 and mY3 RNA and remained reactive to a determinant on Ro60128–285. Absorption with the immunogen depleted the immune sera completely of anti-Golgi complex Ab (inducible only with human Ro60316–335) and anti-La Ab, and reduced substantially Ab to SmD and 70-kDa U1RNP. Mouse rRo60 completely inhibited the immune sera reactivity to La, SmD, and 70-kDa U1RNP. However, La, SmD, and 70-kDa U1RNP preferentially inhibited the antiserum reactivities to these Ags, respectively. Affinity-purified anti-La Ab were reactive with Ro60, La, SmD, and 70-kDa U1RNP. These results provide evidence that a population of the induced autoantibodies recognized determinants shared by these autoantigens. Lack of sequence homology between Ro60316–335 and La, SmD, or 70-kDa U1RNP suggests that these determinants are conformational. Interestingly, similar cross-reactive autoantibodies were found in NZB/NZW F1 sera. Thus, a single molecular mimic may generate Ab to multiple RNP Ags. Furthermore, cross-reactive determinants shared between antigenic systems that are not associated physically (Ro/La RNP and small nuclear RNP) may be important in the generation of autoantibody diversity in systemic lupus erythematosus.

T cell epitope mimicry between Sjögren's syndrome Antigen A (SSA)/Ro60 and oral, gut, skin and vaginal bacteria

This study was undertaken to test the hypothesis that Sjogrens syndrome Antigen A (SSA)/Ro60-reactive T cells are activated by peptides originating from oral and gut bacteria. T cell hybridomas generated from HLA-DR3 transgenic mice recognized 3 regions on Ro60, with core epitopes mapped to amino acids 228-238, 246-256 and 371-381. BLAST analysis identified several mimicry peptides, originating from human oral, intestinal, skin and vaginal bacteria, as well as environmental bacteria. Amongst these, a peptide from the von Willebrand factor type A domain protein (vWFA) from the oral microbe Capnocytophaga ochracea was the most potent activator. Further, Ro60-reactive T cells were activated by recombinant vWFA protein and whole Escherichia coli expressing this protein. These results demonstrate that peptides derived from normal human microbiota can activate Ro60-reactive T cells. Thus, immune responses to commensal microbiota and opportunistic pathogens should be explored as potential triggers for initiating autoimmunity in SLE and Sjögrens syndrome.

Lupus Glomerulonephritis Revisited 2004: Autoimmunity and End-Organ Damage

Histopathology of the kidney and clinical presentation are critical factors in the diagnosis of immune‐mediated glomerulonephritis (GN). The histological manifestations of glomerular injury are shared by multiple underlying mechanisms. Work from our laboratory and from other investigators shows that antinuclear, antihistone or anti‐dsDNA antibodies are neither required nor sufficient for development of lupus GN. In addition, antibody to dsDNA can be generated by mechanisms other than loss of tolerance to chromatin. Genetic analyses demonstrate that although there is some interaction between autoantibody production and renal disease, the phenotypes are regulated by distinct genetic intervals. Furthermore, renal failure is not an essential outcome of the immune‐complex deposition and proliferative lupus GN. These data are also supported by published studies from systemic lupus erythematosus (SLE) patients. The immune regulation of lupus GN is distinct from other organ‐specific diseases and not influenced by CD25+ or NK1.1+ regulatory T cells. Thus, fatal GN may depend upon a kidney‐reactive T‐cell response that, in turn, may be regulated by gender and intrinsic end‐organ factors. The data discussed in this review call for a re‐evaluation of the current paradigms for pathogenesis of SLE. An interactive model separating autoimmunity from end‐organ susceptibility for the pathogenesis of SLE is proposed.

Immune Responses to Small Nuclear Ribonucleoproteins: Antigen-Dependent Distinct B Cell Epitope Spreading Patterns in Mice Immunized with Recombinant Polypeptides of Small Nuclear Ribonucleoproteins

Complex patterns of autoantibody reactivities with the small nuclear ribonucleoproteins (snRNPs) are observed in systemic lupus erythematosus. To investigate the role of individual snRNP components in the initiation and diversification of anti-snRNP Ab responses, we immunized A/J mice with recombinant Smith D (SmD), Smith B (SmB), and A ribonucleoprotein (A-RNP) with alum as adjuvant. Sera at different time points after initial immunizations were analyzed by Western blot and immunoprecipitation assays. In SmD-immunized mice, specific Abs to A-RNP and SmB were generated by 2 mo postimmunization, in addition to the detection of cross-reactive Abs between the immunogen and other snRNPs. Whereas Abs reactive with the immunogen decreased by 5 mo, Abs capable of immunoprecipitating A-RNP and SmB increased. In SmB-immunized mice, specific Abs to A-RNP were readily detectable, in addition to cross-reactive Abs. In contrast, A-RNP-immunized mice had only cross-reactive Abs to SmB without detectable Abs to SmD. However, in these mice, specific Abs to the 70-kDa protein were generated. Abs, which precipitated the native snRNP particle, were generated in all three groups of the immunized mice. Our results show that different initiating Ags from the same multiprotein antigenic complex induce distinct patterns of epitope spreading to proteins within that complex. These data have significant implications for the mechanisms of autoantibody diversification in systemic lupus erythematosus.

Mesangial pathology in glomerular disease: targets for therapeutic intervention

The glomerulus is the filtration unit of the kidney. Disruption of glomerular function may be caused by primary glomerular pathology or secondary to systemic diseases. The mesangial, endothelial and epithelial cells of the glomerulus are involved in most pathologic processes. Animal models provide an understanding of the molecular basis of glomerular disease. These studies show that mesangial cells are critical players in the initiation and progression of disease. Therefore, modulation of mesangial cell responses offers a novel therapeutic approach. The complex architecture of the kidney, specifically the renal glomerulus, makes targeted drug delivery especially challenging. Targeted delivery of therapeutic agents reduces dose of administration and minimises unwanted side effects caused by toxicity to other tissues. The currently available modalities demonstrating the feasibility of mesangial cell targeting are discussed.

Severe Focal Sialadenitis and Dacryoadenitis in NZM2328 Mice Induced by MCMV: A Novel Model for Human Sjögren’s Syndrome

The genetic and environmental factors that control the development of Sjögren’s syndrome, an autoimmune disease mainly involving the salivary and lacrimal glands, are poorly understood. Viruses which infect the glands may act as a trigger for disease. The ability of sialotropic murine CMV (MCMV) to induce acute and chronic glandular disease was characterized in an autoimmune-prone mouse strain, NZM2328. MCMV levels were detectable in the salivary and lacrimal glands 14–28 days after i.p. infection and correlated with acute inflammation in the submandibular gland. After latency, virus was undetectable in the glands by PCR. At this stage, NZM2328 female mice developed severe chronic periductal inflammation in both submandibular and lacrimal glands in contrast to the much milder infiltrates found in female B6-lpr and male NZM2328. The focal infiltrates consisted of CD4+ and B220+ cells as opposed to diffuse CD4+, CD8+, and B220+ cells during acute infection. Salivary gland functional studies revealed a gender-specific progressive loss of secretory function between days 90 and 125 postinfection. Latent MCMV infection did not significantly affect the low incidence of autoantibodies to Ro/SSA and La/SSB Ags in NZM2328 mice. However, reactivities to other salivary and lacrimal gland proteins were readily detected. MCMV infection did not significantly alter the spontaneous onset of kidney disease in NZM2328. Thus, chronic inflammation induced by MCMV with decreased secretory function in NZM2328 mice resembles the disease manifestations of human Sjögren’s syndrome.