The contribution of NZW genes to lupus-like disease in (NZB x NZW)F1 mice

Lupus susceptibility loci in New Zealand mice

Susceptibility to systemic lupus erythematosus has been unequivocally established to be an inherited trait, but the exact genes and how they confer susceptibility remain largely unknown. In this study of (NZB x NZW)F2 intercross mice, we used linkage analysis of markers covering > 90% of the autosomal genome and identified eight susceptibility loci (Lbw1 to -8, chromosomes 17, 4-7, 18, 1, 11, respectively) associated with antichromatin autoantibody production, glomerulonephritis, and/or mortality. Only one locus, the major histocompatibility complex, was linked to all three traits. Two other loci were associated with both glomerulonephritis and mortality, whereas the remaining loci were linked to one of the above traits. Two additional loci (Sbw1 and -2) that contributed to splenomegaly were also identified. The Sbw2 locus mapped to the identical region as Lbw2, a locus on chromosome 4 linked to glomerulonephritis and mortality, suggesting a single locus with pleiotropic effects. The results indicate that the immunopathologic features of lupus are affected by distinct, but additive, genetic contributions. Studies to determine the nature of the genes associated with these loci should help define the genetic mechanisms involved in this systemic autoimmune disease.

In vivo induction of IgG anti-DNA antibody by autoreactive mixed haplotype A beta z/A alpha d MHC class II molecule-specific CD4+ T-cell clones

We characterized autoreactive T-cell clones derived from (NZB x NZW)F1 (B/WF1) mice. These autoreactive T-cell clones are shown to be CD4+ by immunofluorescence staining and to belong to Th2 type by cytokine release assay. Specificity analysis revealed the existence of mixed haplotype A beta z/A alpha d major histocompatibility complex (MHC) class II molecule-specific T-cell clones as well as A beta z/A alpha z- or A beta d/A alpha d-specific T-cell clones. Some but not all of the mixed haplotype A beta z/A alpha d-specific autoreactive T-cell clones showed strong activity to induce IgG anti-DNA antibody production upon transfer to young (4-month-old) B/WF1 mice, indicating that T cells with these specificities might be involved in B/WF1 autoimmunity.

Holes in the T cell repertoire to myelin basic protein owing to the absence of the D beta 2-J beta 2 gene cluster: implications for T cell receptor recognition and autoimmunity

Models of T cell recognition suggest that amino acid residues in the CDR3 region of the T cell receptor (TCR) alpha or beta chain directly contact the major histocompatibility complex-bound peptide, and thus are crucial for providing peptide specificity. T cells derived from B10.PL or PL/J mice of H-2u haplotype, use only D beta 2 and J beta 2 gene segments in the recognition of the dominant determinant, Ac1-9/Au, of myelin basic protein (MBP). New Zealand White (NZW) mice, with identical class II H-2u genes (I-A and I-E), carry an 8.8-kb deletion in their TCR beta chain locus encompassing D beta 2 and J beta 2 gene segments. How does this deletion of the crucial D beta 2-J beta 2 region in NZW mice influence specific responses to Ac1-9/Au as well as to other known Au or Eu determinants of MBP? We found that these mice respond very poorly to the dominant Ac1-9/Au and to the subdominant 31-50/Eu determinant in in vitro proliferation assays as well as in their in vivo capacity to induce experimental autoimmune encephalomyelitis. This loss of response is apparently owing to the absence of high avidity TCRs with essential CDR3 residues contributed by D beta 2 or J beta 2 gene segments. These data reveal constraints in the recognition of certain antigenic structures, and further support a TCR-recognition model in which CDR3 residues of the TCR alpha and beta chains constitute the antigenic peptide-binding sites on the TCR molecule. Implications for autoimmune manifestations contributed by NZW genes in (NZB x NZW)F1 disease are also discussed.

Genetic analysis of the NZB contribution to lupus-like autoimmune disease in (NZB x NZW)F1 mice

Lupus-like autoimmunity in (NZB x NZW)F1 mice is frequently marked by the development of a severe and fatal renal disease. Genes from both NZB and NZW parents are required for the full expression of disease. We applied a mapping technique based on polymorphism in simple sequence repeats to the analysis of (NZB x NZW)F1 x NZW backcross mice to determine the NZB genetic contribution to disease. The results show that a single NZB locus or tightly linked group of loci on the distal part of chromosome 4 provides the strongest association with renal disease and death. This locus, designated here as nba-1 (New Zealand Black autoimmunity), lies distal to the locus elp-1, 60-70 centimorgans from the centromere. It is of interest that a gene encoding a receptor for tumor necrosis factor maps to the vicinity of this disease-associated gene.

Prolonged and effective blockade of tumor necrosis factor activity through adenovirus-mediated gene transfer

A chimeric protein capable of binding and neutralizing tumor necrosis factor (TNF) and lymphotoxin was expressed in mice transduced with a replication-incompetent adenoviral vector into which a TNF inhibitor gene had been engineered. Within 3 days following the injection of 10(9) infectious particles, the TNF inhibitor concentration exceeded 1 mg/ml of plasma; this level of expression was maintained for at least 4 weeks, and detectable TNF inhibitory activity was measured 6 weeks after injection of the recombinant virus. Introduction of the artificial gene produced a phenotypic effect comparable to homozygous deletion of the 55-kDa TNF receptor, in that animals were rendered highly susceptible to infection by Listeria monocytogenes, whereas control animals receiving a replication-incompetent virus coding for beta-galactosidase were capable of resisting Listeria challenge. Adenovirus-mediated transfer of a gene encoding a TNF inhibitor offers a practical means of imposing effective, long-term blockade of TNF activity in vivo for investigational and therapeutic purposes.

Analysis of tumor necrosis factor promoter responses to ultraviolet light

Ultraviolet (UV) light induces the biosynthesis of chloramphenicol acetyltransferase (CAT) in the skin of mice bearing the CATTNF reporter transgene. Moreover, nuclear run-on assays indicate that UV light induces transcription of the TNF gene in RAW 264.7 macrophages. These observations suggest that the TNF gene (and/or its mRNA product) responds to signals elicited by UV light. To identify transcriptional UV response elements within the TNF promoter, and to determine whether a posttranscriptional response might also exist, a series of reporter constructs using a CAT coding sequence attached to various portions of the TNF promoter and 3' untranslated region were devised and transfected into several cultured cell lines. All cells tested were found to be UV responsive, and in NIH 3T3 cells, induction was found to depend upon two general regions of the promoter. The more distal region encompassed nucleotides (nt) -1059 through -451 with respect to the cap site, while the more proximal region spanned nt -403 through -261. A negative element, blocking the UV response, was interposed (nt -451 through -403). As with the response to LPS, the response to UV irradiation appears to involve translational activation in macrophages. However, the UV and LPS signaling pathways have little in common with one another, as indicated by three observations. First, no difference in responsiveness was observed on comparison of TNF gene induction in macrophages derived from C3H/HeN as opposed to C3H/HeJ mice. Second, cell fusion studies showed that while the LPS signaling pathway is extinguished by fusion of RAW 264.7 cells with NIH 3T3 cells, the UV signaling pathway remained intact. Finally, induction did not depend upon the NF-kappa B binding sites that are known to be required for LPS response in macrophages, since mutation of these sites did not impair the UV response.

Histocompatibility complex gene products and exposure to oestrogen: two independent disease accelerating factors in murine lupus

A number of studies have demonstrated that oestrogen exerts a significant impact on the course of experimental autoimmune diseases. Exposure to oestrogen aggravates SLE glomerulonephritis whereas the opposite outcome has been demonstrated in experimental arthritis, vasculitis, thyroiditis, and sialadenitis. In this report we have analysed the respective impact of H-2z linked gene products and long-term treatment with physiological doses of oestradiol on clinical and immunological variables in castrated backcrosses of lupus prone NZB/W and NZB mice. Our results demonstrate that H-2z linked gene products accelerate B-cell activation and stimulate autoantibody production resulting in aggravation of glomerulonephritis and precocious death in renal failure. These H-2z linked gene products do not influence T-cell mediated sialadenitis. Irrespectively of the H-2 haplotype of the mice, administration of oestrogen resulted in intense polyclonal B cell activation and aggravation of glomerulonephritis. However, exposure to oestrogen resulted in amelioration of sialadenitis. Notably, our result indicates that B-cell activation achieved by oestrogen and H-2z gene linked products, respectively is mediated by independent mechanisms. In addition, we have developed a predictive in vivo test that permits forecasts regarding efficiency of oestrogen treatment for suppression of T-cell mediated lesions. Using this test procedure in young, clinically healthy SLE mice we have been able to prove that animals displaying suppressed delayed type hypersensitivity (DTH) after short-term oestrogen exposure showed significantly lower long-term morbidity regarding development of sialadenitis upon continuous treatment with physiological doses of oestradiol.

Genetic and immunological mechanisms in the pathogenesis of systemic lupus erythematosus

Recent research in systemic lupus erythematosus and animal models of lupus has provided new insight into the pathogenesis of this complex autoimmune disease. Progress has been made towards understanding the genetic contributions to disease susceptibility and induction, as well as towards elucidation of the lymphocyte abnormalities involved in pathogenic autoantibody production.

Development of autoimmune disease in SCID mice populated with long-term "in vitro" proliferating (NZB x NZW)F1 pre-B cells

Pre-B cell lines proliferating for several months on stromal cells in the presence of interleukin 7 (IL-7) were established from fetal liver of (NZB x NZW)F1 mice. They express the B lineage-specific markers PB76, B220, and VpreB, but do not express surface immunoglobulin (sIg). Upon removal of IL-7 from the culture, they differentiate to sIg+ B cells that can then be stimulated by lipopolysaccharide to become IgM-secreting cells. Transfer of these pre-B cell lines into SCID mice leads to hypergammaglobulinemia of IgM (600-900 micrograms/ml), IgG2a (1-3 mg/ml), and IgG3 (300-500 micrograms/ml) for the next 3-5 mo. The spleen appears populated with (NZB x NZW)F1-derived pre-B cells, few B cells, and many IgM and/or IgG-producing plasma cells. In contrast, SCID mice populated with pre-B cell lines of normal (C57BL/6 x DBA/2)F1 mouse fetal liver develop normal levels of serum IgM (approximately 100-300 micrograms/ml), almost no detectable levels of IgG, and no plasma cell hyperplasia. The (NZB x NZW)F1 pre-B cell-populated SCID mice contain elevated serum titers of IgG antinuclear autoantibodies, but no retroviral gp70-specific nor erythrocyte-specific autoantibodies. Up to 20% of the SCID mice develop proteinuria as a consequence of IgG deposits in the kidney glomeruli during a 7-mo period of observation. All signs of autoimmune disease seen in these mice are independent of the sex of the SCID host. This experimental system provides a distinction between the disease-determining (NZB x NZW)F1 genes, which are expressed in the B lymphocyte lineage and cause the development of the disease, from those expressed in other cell lineages which only modulate its progression.

Acquisition of autoimmunity genes by New Zealand mice is associated with natural resistance to infection by mycobacteria

New Zealand (NZ) mouse strains comprise both autoimmune and non-autoimmune animals: NZ black (NZB) mice and the F1 hybrid (NZB/W) of NZB and NZ white (NZW) mice show spontaneous autoimmune disease by 6 months of age and die before the first year of age from renal disease, while NZW mice do not show autoimmune disorders. We investigated whether the autoimmunity-prone NZ animals (NZB and NZB/W) differ from the non-autoimmune NZW mice in susceptibility/resistance to mycobacterial infection. The three groups of NZ mice were infected by intraperitoneal inoculation of 10(8) colony forming units (cfu) of Mycobacterium avium. The M. avium infection was induced in 3-month-old mice (i.e., before NZB and NZB/W mice develop autoimmune disease) and studied for 4 months. Infected NZB and NZB/W mice showed evidence of renal disease at 2 and 4 months of infection (but not at 1 month). The non-autoimmune NZW mice were found to be susceptible to M. avium since they allowed massive proliferation (4-5 log growth) of the bacilli in liver and spleen. In contrast, both groups of autoimmunity-prone mice (NZB and NZB/W) were resistant to M. avium since their mycobacterial loads remained below the value of the initial inoculum. We conclude that in NZ mice the acquisition of autoimmunity genes is associated with expression of natural resistance to mycobacterial infection. This is consistent with the view that autoimmunity genes may have been evolutionarily selected because of their association with increased resistance of the host to infections by intracellular parasites.

Studies on the role of tumor necrosis factor in murine and human autoimmunity

We have analyzed the roles of tumor necrosis factor alpha (TNF-alpha) in human systemic lupus erythematosus (SLE) and murine models of lupus as well as in type 1 diabetes in NOD mice. These studies suggest an important role for TNF-alpha in the pathogenesis of autoimmune disease. Rather than being involved mainly in the effector arm of the inflammatory process of autoimmune organ destruction, our data suggest a primary involvement in some of the basic mechanisms of the autoimmune process. Evidence has been presented that emphasizes the possibility of the involvement of this cytokine in the genetic predisposition to SLE. The data may imply that the effect of TNF on the immune system may be more relevant to the pathogenesis of the autoimmune disease than direct local effects at some target organs. Based on the data presented, one should be cautious in extrapolating the effects of this cytokine in various in vitro systems to the in vivo situation.

cis and trans elements differ among mouse strains with high and low extrahepatic complement factor B gene expression

Factor B (Bf), an enzyme of the alternative pathway of complement activation, is one of four major histocompatibility complex (MHC) class III genes. To ascertain the genetic mechanism for tissue-specific constitutive and regulated expression of Bf, we sequenced the regulatory regions 5' of the gene from mice of different H-2 MHC haplotypes and assessed trans-acting factors, specific DNA binding nucleoproteins, in liver and kidney. Striking tissue-specific differences in constitutive expression of Bf were demonstrated in mice of H-2f or H-2z haplotypes when compared with H-2d or H-2u (kidney and intestinal Bf in H-2d or H-2u much greater than H-2f or H-2z). These differences correlated with a point nucleotide substitution 3 bp downstream of the upstream Bf initiation site that affects interaction with a DNA binding protein. This and additional cis differences localize the sequence substitutions responsible for previously identified restriction fragment length polymorphisms among inbred mouse strains and also reveal two previously unrecognized polymorphisms generated by SmaI and HinfI digestion. Evidence for differences in trans was found in a comparison of DNA binding nucleoproteins from kidney, but not liver, of B10.PL when compared with B10.M. These data, together with the high degree of sequence homology between human and mouse Bf 5' flanking regions, should prompt a search for polymorphic restriction sites and cis binding elements in the Bf promoter that could serve as markers of human MHC-associated renal pathology and variants in local MHC class III gene expression.

Background genes mediate the development of autoimmunity in (NZB x PL/J)F1 or (NZB x BIO.PL)F1 mice

The (NZB x NZW)F1 mouse develops a lupus-like disease including anti-double-stranded DNA antibodies and renal disease. It has been demonstrated that genes linked to the H-2 locus contributed by NZW correlate with development of this disease. We investigated whether mice with identical class II molecules but different background genes could contribute to autoimmunity when crossed with NZB. We report that two strains, PL/J and BIO.PL, when crossed to NZB, do not result in F1 with autoimmunity. Therefore, background genes present in NZW but not in PL/J or BIO.PL contribute to the development of disease.

T cell receptor beta diversity and joining segments in the NOD mouse

Pancreatic beta-cell autoantigen recognition by the immune system appears to be a critical event in the evolution of insulin dependent diabetes. Immune recognition involves antigen presentation by macrophages and subsequent antigen-peptide-class II MHC recognition by T cell receptors (TCR). Using the NOD mouse as a model for human IDD, we hypothesized that germline variability in the D beta nod and/or J beta nod segments could contribute to beta cell autoimmunity by influencing the specific peptides that are recognized. As an initial approach to our hypothesis, we sought to compare these segments to other strains of mice in search of genetic polymorphisms as reported in NZW mice. The germ line TCR beta nod gene did not display evidence of an expansion or contraction in the number of D beta nod or J beta nod segments at the level of resolution provided by restriction fragment length polymorphism analysis. The absence of such polymorphisms suggests that D beta nod or J beta nod segments are not different from nonautoimmune strains of mice.

Tumor necrosis factor alpha in murine systemic lupus erythematosus disease models: implications for genetic predisposition and immune regulation

Recombinant tumor necrosis factor alpha (TNF-alpha) administration significantly delayed the development of lupuslike nephritis in the New Zealand black x New Zealand white (NZB x NZW)F1 and to a lesser extent in the MRL-lpr/lpr model systems. TNF-alpha treatment was effective when treatment was initiated at 2, 3, or 4 months of age but was ineffective if initiated as late as 6.5 months of age. Treatment of (NZB x NZW)F1 mice for 3 months was more effective than treatment continued for 6 months. Anti-TNF-alpha antibodies did not develop in these mice. Flow microfluorometry analysis showed no major effects on B, T, or monocyte cell population in cells from the peritoneum, spleen, lymph node, and thymus. A decrease in class II Ia expression on macrophages in the peritoneum of TNF-alpha-treated mice was noticed. A correlation between the level of TNF-alpha inducibility in vitro and the effect of TNF-alpha administration in vivo could be shown. Although a limited polymorphism could be shown by restriction fragment length polymorphism, using an amplified (AC)n microsatellite located in the 5' regulatory region of TNF-alpha, a much more extensive interallelic polymorphism was found. The AC microsatellite allele found in NZW mice was unique and different from other lupus strains and nonautoimmune strains. These results have possible implications to the pathogenesis of systemic lupus erythematosus.

The contribution of non-MHC genes to susceptibility to autoimmune diseases

Genetic studies of experimental models of autoimmune diseases, including systemic lupus-like syndromes and organ-specific autoimmunity, provide major information on genetic control of autoimmune diseases. In addition to genes known to be linked to the major histocompatibility complex (MHC), these studies point to multiple genes located outside the MHC that influence the onset and the progression of autoimmune diseases. Identification of these genes and of their interrelationships is now a major task that will be facilitated by recent progress in molecular biology and gene mapping. Among candidate genes, antigen-receptor genes (i.e., immunoglobulin- and T-cell receptor genes) most likely contribute an important part of the autoimmune susceptibility in several of these animal models. Available linkage data suggest a similar involvement of these antigen-receptor genes in several human autoimmune diseases. In addition to a better understanding of pathogenic mechanisms associated with autoimmunity, the knowledge of these disease-predisposing genes is expected to permit a better classification of often complex syndromes as well as the design of new treatments.

Genetic control of inflammatory arthritis and glomerulonephritis in congenic lpr mice and their F1 hybrids

MRL-lpr/lpr mice spontaneously develop a complex immunological disease characterized by glomerulonephritis, inflammatory erosive arthritis and the production of rheumatoid factors (RF) and anti-DNA antibodies. We have previously reported that, of congenic lpr strains, only MRL-lpr/lpr mice develop synovial pathology suggesting that both the lpr gene and another gene(s) in the MRL background are necessary for the development of arthritis. To define further the genetics of arthritis and its relationship to glomerulonephritis and autoantibody production, we studied disease expression in MRL-lpr/lpr and C57BL/6-lpr/lpr mice and their offspring (BM-lpr/lpr and MB-lpr/lpr). At 6 months of age these mice were killed and bled, and their kidneys and knee joints were removed for pathological studies. Fourteen of 28 MB-lpr/lpr mice displayed synovial hypertrophy, while eight of 28 had significant synovial inflammation. BM-lpr/lpr mice showed similar changes: nine of 22 and eight of 22 exhibited synovial hypertrophy and inflammation respectively. Joints from MRL-lpr/lpr mice revealed 13 of 17 with synovial hypertrophy and 12 of 17 with inflammation, while none of 14 B6-lpr/lpr mice had synovial changes. Renal pathology was minimal in the F1 mice with only mild hypercellularity in seven of 21 MB-lpr/lpr and five of 22 BM-lpr/lpr mice. All MRL-lpr/lpr mice, in contrast, had marked glomerular changes with 12 of 17 exhibiting glomerular crescents. Only one F1 mouse had both arthritis and renal abnormalities. IgM RF levels were elevated in all four experimental groups, but did not correlate with the presence or severity of arthritis. IgG RF levels were elevated in the MB-lpr/lpr and MRL-lpr/lpr mice, but did not correlate with the degree of arthritis. These results indicate that renal disease and arthritis develop independently in lpr mice, possibly on a genetic basis, and that the presence and titer of autoantibodies do not correlate with tissue injury.

Analysis of the genetic encoding of oestradiol suppression of delayed-type hypersensitivity in (NZB x NZW) F1 mice

Oestrogen (E2) has been suggested to be responsible for the female preponderance for systemic lupus erythematosus (SLE) and for exacerbations of disease during pregnancy. In lupus-prone (NZB x NZW) F1 (NZB/W) mice, sex hormones also influence disease progression, thus long-term treatment of NZB/W mice with high doses of oestradiol increases the mortality in immune-complex mediated disease. We have previously demonstrated that E2 suppression of delayed-type hypersensitivity (DTH) to oxazolone (OXA) in NZB/W mice is inherited from the healthy NZW (H-2z) and not from the autoimmune NZB (H-2d) parental strain. In this paper we have analysed the influence of E2 on DTH and antibody responses to OXA in backcrosses of NZB/W mice and the NZB and NZW parental strains. Suppressed DTH was found in 15/16 (94%) of female (NZB/W x NZW) F1 (NZB/W/W) mice treated with E2. In contrast, only 32/36 (51%) of (NZB/W x NZB)F1 (NZB/W/B) mice treated with E2 displayed suppressed DTH reactivity. These two findings are compatible with a single, rather than multiple, dominant gene inherited from the NZW strain encoding for E2-mediated suppression of DTH in NZB/W mice. FACS analysis, using a monoclonal antibody recognizing the H-2z but not the H-2d locus, identified the H-2 expression (H-2dd and H-2dz) of the NZB/W/B backcrosses and revealed that E2 suppression of DTH is not linked to the H-2 haplotype of the backcrosses. Furthermore, E2 treatment of NZB/W/W mice, but not of NZB/W/B mice, significantly enhanced the serum levels of anti-OXA antibodies of both IgG and IgM classes. Based on our results it is tempting to speculate whether similar genetic factors for E2 sensitivity of the immune system may be of importance for the female predominance of human SLE.

No association with germline T cell receptor beta-chain gene alleles or haplotypes in Swedish patients with multiple sclerosis

Multiple sclerosis (MS) has been reported to be associated with restriction fragment length polymorphism (RFLP)-defined alleles of the T cell receptor (TcR) alpha- and beta-chain genes. One hundred patients with MS, 23 with primarily chronic progressive MS and 77 with relapsing/remitting MS, as well as 100 controls were investigated with RFLP analysis of the V beta 8, V beta 11 and C beta TcR gene segments. No association was found with allelic patterns or, contrary to a previous report (Beall et al. (1989) J. Neuroimmunol. 21, 59-66), TcR beta-chain gene haplotypes. Subgrouping of patients according to clinical form of disease or MS-associated HLA class II alleles also failed to show associations to TcR beta-chain RFLPs. Thus, our results fail to confirm that TcR beta-chain gene haplotypes confer susceptibility to MS.

Contribution of the gene linked to the T cell receptor beta chain gene complex of NZW mice to the autoimmunity of (NZB x NZW)F1 mice

We have investigated the contribution to the autoimmune disease of (NZB x NZW)F1 (NZB/W) mice made by the T cell receptor beta (TcR beta) chain gene complex, or genes linked to it, that are derived from the NZW strain. For this we developed the NZW.TcR beta NZB strain, a NZW congenic line carrying the TcR beta of NZB type, and produced NZB x NZW.TcR beta NZB (NZB/W.TcR beta NZB)F1 mice. We compared the amounts of anti-DNA and anti-histone antibodies and also the severity of lupus nephritis in these mice with those in the original NZB/W F1 mice. We obtained evidence for significantly lower serum levels of autoantibodies to double-stranded and single-stranded DNA and histone, and a later onset and a lower incidence of proteinuria in the NZB/W.TcR beta NZB F1 mice than in the original NZB/W F1 mice. These findings clearly indicate that the gene(s) within or closely linked to the TcR beta chain gene complex on chromosome 6 of the NZW strain acts to intensify the feature of systemic lupus erythematosus in the NZB/W F1 strain. The significant relationship of this finding to the strict dependency of NZB/W F1 disease on the H-2d/H-2z heterozygosity is discussed.

The contribution of I-Abm12 to the production of autoantibodies to dsDNA

The development of IgG autoantibodies to dsDNA in NZBxNZW F1 (NZB/W) and NZBxSWR F1 (SNF1) mice have been linked to specific alleles of MHC class II genes contributed by the NZW and SWR parents respectively. Recently, our laboratory has shown that the introduction of the bm12 mutation into NZB mice (NZB.H-2bm12) results in mice which are phenotypically similar to NZB/W F1 mice and, in particular, develop IgG anti-dsDNA antibodies. A variety of immune abnormalities have been described in autoimmune NZB (H-2d) mice. It is, however, unclear at present, whether all these abnormalities are due to the influence or effect of a single set of linked genes or due to multiple genes. It was reasoned that NZB.H-2bm12 mice provide a unique opportunity to examine this issue. Specifically, we bred a series of five different F1 colonies of mice: (a) NZB.H-2bm12/b F1; (b) NZB.H-2bm12/d F1; (c) NZB-H-2b/d F1; (d) NZB-H-2bm12 x B6.C-2bm12 F1 (NZB/B6.H-2bm12 F1); and (e) NZB x B6.C-H-2bm12 F1 (NZB/B6.H-2d/bm12 F1) mice. All groups of mice were serially followed for the appearance of IgM and IgG anti-ssDNA and anti-dsDNA antibodies, splenic CFU-B, spontaneous secretion of IgM, FMF analysis, proteinuria and survival. We report herein that H-2bm12 genes have a dominant influence on the appearance of IgG anti-dsDNA antibodies. In contrast, antibodies to ssDNA, IgM secreting cells, CFU-B and Ly-1 B cells are linked to genes from the NZB background. Finally, we particularly note an absence of IgG antibodies to dsDNA in NZB-H-2b/d F1 mice.

Association of psychiatric manifestations with antibodies to ribosomal P proteins in systemic lupus erythematosus

PURPOSE

The goal of this study was to determine whether elevated serum levels of antibodies to ribosomal P proteins (anti-P antibodies) are associated with neuropsychiatric manifestations in patients with systemic lupus erythematosus (SLE). Additional experiments examined characteristics of these antibodies that might be associated with pathogenicity.

PATIENTS AND METHODS

A large number of serum samples were collected from patients with SLE, control subjects with other rheumatic diseases, and normal individuals. At the time serum samples were obtained, patients with SLE were categorized according to the presence of psychosis, depression, and other manifestations of central nervous system (CNS) involvement. Serum anti-P antibody activity was quantitated by an enzyme-linked immunosorbent assay utilizing a synthetic peptide corresponding to the major P protein epitope.

RESULTS

In a group of 79 normal individuals, mean (+/- SE) IgG anti-P activity was 0.01 +/- 0.003 and no individuals had values greater than 3 SD above the mean. Similar results were obtained measuring IgM anti-P activity. Normal levels were found in all sera from 21 patients with rheumatoid arthritis. Of 119 patients demonstrating various patterns of antinuclear and anticytoplasmic antibody activity, elevated anti-P levels were found only in patients with SLE. Overall, 19% of 269 patients with SLE demonstrated elevated levels of IgG or IgM anti-P antibodies, including 14% of 187 patients without and 29% of 82 patients with neuropsychiatric manifestations. The frequency of positive test results varied greatly depending on the nature of the CNS involvement. The frequency in patients with severe depression (n = 8) and psychosis (n = 29) was 88% and 45%, respectively, compared with only 9% in patients with nonpsychiatric neurologic disease (n = 45). For the entire SLE group, the odds ratio for the association of anti-P antibodies and severe psychiatric manifestations was 7.63 with a 95% confidence interval of 3.61 to 16.14. In a review of 187 patients with SLE originally classified as not having severe psychiatric disease, seven of 10 patients being treated with antidepressant medications had elevated levels of anti-P antibodies. In serial studies, the serum level of anti-P antibodies appeared to correlate with the activity of psychiatric disease and did not correlate with the activity of other manifestations of SLE. Anti-P antibodies in nearly all patients were IgG and directed primarily to the C-terminal 11 amino acids of the P protein. No difference in these characteristics was observed when patients with and without psychiatric manifestations were compared. Paired serum and cerebrospinal fluid (CSF) samples were also obtained from eight patients with active neuropsychiatric disease. Even when expressed as a fraction of the total IgG present, anti-P activity was markedly lower in CSF than in serum.

CONCLUSIONS

Elevated levels of autoantibodies to the C-terminal region of ribosomal P proteins appear to be a specific marker for SLE, and are associated with both severe depression and psychosis in this disease. This assay is easily reproducible and may help distinguish SLE-induced psychiatric disease from that caused by other processes.

Ionic binding characteristics of monoclonal autoantibodies to DNA from NZB.H-2bm12 mice

NZB (H-2d) mice are well known for the production of IgM autoantibodies to ssDNA. However, an F1 cross between NZB and either NZW or SWR mice is required to produce IgG nephritogenic antibodies to dsDNA and glomerulonephritis. The contribution of parental class II loci in the hybrid mice is clearly important to the development of anti-dsDNA antibodies. In contrast, NZB mice congenic with the Iabm12 mutation develop IgG autoantibodies to dsDNA despite being homozygous for Ia. As a part of our effort to examine the mechanisms of disease development in NZB.H-2bm12 mice, we have generated a panel of monoclonal antibodies against nucleic acids. A subgroup of these antibodies exhibited strong electrostatic interaction with nucleic acids as evidenced by inhibition of their binding by a moderate increase in ionic strength. Interestingly, the effect of salt was either all or none; e.g., antibodies were either markedly inhibited or virtually unaffected. The importance of this ionic interaction was highlighted by analysis of DNA binding of antibodies from serum and nephritic kidneys of NZB.H-2bm12 mice. Antibodies specific for ssDNA, which are common in NZB mice and not associated with nephritic lupus, are largely unaffected by salt. However, serum and kidney eluted IgG antibodies specific for dsDNA were markedly inhibited by salt. We postulate that B cell clones whose antibodies exhibit electrostatic interaction with DNA are preferentially expanded during the course of lupus in NZB.H-2bm12 mice and that such antibodies contribute significantly to glomerulonephritis.

Association between a T cell receptor restriction fragment length polymorphism and systemic lupus erythematosus

The present study was designed to test the possibility that T cell receptor genes are associated/linked to those involved in systemic lupus erythematosus (SLE). Genomic DNA was isolated from 31 unrelated Caucasian SLE patients, 34 unrelated Caucasian normals, 5 multiplex American Caucasian SLE families, 9 multiplex Mexican SLE families, and 13 unrelated Mexican normals. The DNA was digested with Pst I, electrophoresed, and transferred to membranes by the Southern blot method. The blots were probed with a cDNA probe for the alpha chain of the T cell receptor. 13 polymorphic RFLP patterns were recognized. 1.3- and 3.0-kb band pairs were observed in 15 of 31 of American Caucasian patients and 4 of 34 American Caucasian controls (chi square, 8.81; P less than 0.002; relative risk, 7); there was no association of any RFLP pattern with Mexican SLE. The cDNA probe was cut with Rsa I, EcoR I, and Ava II into fragments corresponding to the V, J, C, and 3'UT regions. Only the fragment corresponding to the constant region reacted with the 1.3/3.0-kb band pair. These observations suggest that a genetic marker of the constant region of the alpha chain of the T cell receptor is associated with genes involved in SLE.

Polyclonal B cell activation in lupus-prone mice precedes and predicts the development of autoimmune disease

Polyclonal B cell activation is an early feature of autoimmune disease in humans and mice with systemic lupus erythematosus. The contribution of polyclonal activation to the progression of autoimmunity is unclear, however, since it precedes the development of end-organ damage by months or years. To examine this issue, 109 autoimmune-prone (NZB X NZW)F1 X NZB backcross mice were hemi-splenectomized at 10 wk and the number and antigenic specificity of their Ig-secreting B cells quantitated by ELISA spot assay. Of the 61 mice that had polyclonally increased numbers of Ig-secreting cells/spleen, 31 died by 6 mo. In contrast, 0/48 backcross mice with normal numbers of Ig-secreting B cells at 10 wk died over the same period (P less than 0.001). Polyclonally activated mice also developed proteinuria earlier and more frequently than littermates with normal numbers of Ig-secreting cells (P less than 0.001). As adults, backcross mice with proteinuria expressed repertoires skewed towards the production of anti-DNA antibodies. At 10 wk these same mice expressed repertoires marked by polyclonal activation rather than preferential anti-DNA production. These findings indicate that autoimmune disease in SLE is accompanied by the autoantigen-driven production of autoantibodies but is preceded and predicted by polyclonal B cell activation.

T cell receptor V beta genes expressed by IgG anti-DNA autoantibody-inducing T cells in lupus nephritis: forbidden receptors and double-negative T cells

In the (SWR x NZB)F1 (SNF1) model of lupus nephritis, pathogenic variety of IgG anti-DNA autoantibodies are induced by certain T helper (Th) cells that are either CD4+ or CD4-CD8- (double negative; DN) in phenotype. From the spleens of eight SNF1 mice with lupus nephritis, 149 T cell lines were derived and out of these only 25 lines (approximately 17%) were capable of augmenting the production of pathogenic anti-DNA autoantibodies. Herein, we analyzed the T cell receptor (TcR) V beta genes used by 16 such pathogenic autoantibody-inducing Th cell lines. Twelve of the Th lines were CD4+ and among these five lines expressed V beta 8 (8.2 or 8.3). The V beta 8 gene family is contributed by the NZB parent to the SNF1 mice, since it is absent in the SWR parental strain. Three other CD4+ Th lines expressed V beta 4, another was V beta 2+ and one line with poor autoantibody-inducing capability expressed V beta 1. Four autoantibody-inducing Th lines from the SNF1 mice had a DN phenotype and these lines were also autoreactive, proliferating in response to syngeneic spleen cells. Among these DN Th lines, two expressed V beta 6 and one expressed V beta 8.1 TcR. Both of these are forbidden TcR directed against Mls-1a (Mlsa) autoantigens expressed by the SNF1 mice and such autoreactive T cells should have been deleted during thymic ontogeny. Thus, the DN Th cells of non-lpr SNF1 mice are different from the DN cells or MRL-lpr which lack helper activity and do not express forbidden TcR. The spleens of 6 out of 19 nephritic SNF1 animals tested also showed an expansion of forbidden autoreactive TcR+ cells that were mainly DN. Two of these animals expressed high levels of V beta 6 (anti-Mlsa) and V beta 11 (anti-I-E) TcR+ cells, three others had high levels of V beta 11+ cells alone and one animal had an expanded population of V beta 17a+ (anti-I-E) cells. The I-E-reactive TcR again should have been eliminated in the SNF1 thymus, since they express I-E molecules contributed by the NZB parent. The SWR parents of SNF1, are I-E-; moreover, they lack the V beta 11 gene but they express V beta 17a in peripheral T cells. Whereas the NZB parents are I-E+, they lack a functional V beta 17a gene and they delete mature V beta 11+ T cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Autoimmune diseases: the failure of self tolerance

The ability to discriminate between self and nonself antigens is vital to the functioning of the immune system as a specific defense against invading microorganisms. Failure of the immune system to "tolerate" self tissues can result in pathological autoimmune states leading to debilitating illness and sometimes death. The induction of autoimmunity involves genetic and environmental factors that have focused the attention of researchers on the trimolecular complex formed by major histocompatibility complex molecules, antigen, and T cell receptors. Detailed molecular characterization of these components points to potential strategies for disease intervention.

A polymorphic microsatellite in the tumor necrosis factor alpha promoter identifies an allele unique to the NZW mouse strain

We have amplified a (CA)n:(GT)n microsatellite from the TNF promoters of a panel of mouse strains using the polymerase chain reaction. The length of the microsatellites was polymorphic, with eight alleles observed among 15 inbred strains bearing seven distinct H-2 haplotypes, and four outbred strains. In B10 congenic strains, the TNF allele detected by microsatellite polymorphism segregated with the MHC, and in recombinant haplotypes (NOD, NZW), it segregated with H-2D. The TNF allele found in the NZW strain (H-2z) was distinct from those of all other haplotypes, consistent with the hypothesis that this strain may carry a genetic defect in TNF production.

Correlations of autoimmunity with H-2 and T cell receptor beta chain genotypes in (NZB X NZW) F2 mice

Accelerated autoimmunity as expressed by the classical autoimmune strain mouse (NZB x NZW)F1 is thought to be the result of major histocompatibility complex (MHC)-associated NZW genes acting on a genetic predisposition for autoimmunity as expressed by the NZB mouse. To evaluate more accurately both H-2 and T cell receptor (TcR) beta chain involvement in F1 disease, we studied the segregation of NZB (H-2d, TcRB) and NZW (H-2z, TcRW) haplotypes of these genetic elements and the development of autoimmunity in (NZB x NZW)F2 generation mice. F2 mice with the H-2d/z genotype lived shorter average life-spans and expressed elevated levels of antibodies to gp70, ssDNA and dsDNA, while those with the TcRW/W genotype (homozgous for the NZW TcR deletion) expressed elevated levels of autoantibodies but had relatively long life-spans. On the other hand, mice with the TcRB/B genotype (homozygous for the NZB TcR) produced consistently low levels of autoantibodies but died at an early age. The most severely affected F2 population were the mice carrying both the TcRB/B and H-2d/z alleles. These mice died on an average within the first 5 months of life, but produced the lowest levels of antibodies to gp70, single-stranded DNA and double-stranded DNA. These data confirm the contribution of NZW H-2-linked genes to accelerated autoimmunity in the F1 hybrid and, furthermore, define NZB TcR-linked components as primary developers of this phenomenon. They also suggest a limited, if any, contribution of both the NZW TcR deletion and traditional autoantibodies to F1 accelerated autoimmunity.

Sequence of I-E genes from autoimmune New Zealand white mice

Autoimmune New Zealand white (NZW) mice contribute to (New Zealand black x New Zealand white)F1 mice 1 or more major histocompatibility complex-linked genes that strongly correlate with susceptibility to murine lupus. The NZW class II major histocompatibility complex genes, I-E alpha and I-E beta, were cloned and sequenced and found to differ from normal B10.PL (H-2u) mice by 3 amino acids in the first domain of the I-E beta subunit. Of these differences, the arginine at position 72 of NZW mice could be an important disease determinant since it lies in a predicted antigen-binding cleft.

Anti-Ro(SSA) autoantibodies are associated with T cell receptor beta genes in systemic lupus erythematosus patients

Several of the heterogeneous clinical manifestations of systemic lupus erythematosus have been associated with specific autoantibodies. Associations between HLA class II antigens and autoantibodies to the ribonucleoproteins Ro(SSA) and La(SSB) have been reported in these patients. Because HLA class II molecules present antigen to T cell receptors (TCRs), we have searched for a TCR gene associated with the production of anti-Ro(SSA) antibodies. A pair of restriction fragment length polymorphisms (RFLPs), one of which hybridizes to the TCR constant region C beta 1 and the other to the C beta 2 gene, has been identified, suggesting these may be genotypic markers for an extended region of the TCR beta locus. This RFLP pair occurs in 76% of patients with Ro(SSA) precipitins, 84% of anti-Ro(SSA)-positive patients lacking La(SSB) precipitins, but only 41% of the patients lacking both precipitins (P = 0.0004). This disproportionate occurrence in a subset of lupus patients indicates that these RFLPs are not disease susceptibility markers, but rather are important markers for TCR genes whose products are involved in the production of anti-Ro(SSA) antibodies. The majority of patients who have these RFLPs and HLA class II antigens previously associated with the anti-Ro(SSA) response make this antibody, suggesting that interactions between products of these loci occur in response to Ro(SSA).

Self-reactive T cells in murine lupus: analysis of genetic contributions and development of self-tolerance

Our understanding of the immune mechanisms that lead to systemic lupus erythematosus has been greatly advanced by the availability of murine models which display both serological and clinical features of the human disease. Studies have demonstrated that CD4+ T cells are required for the full expression of disease in these mice. (NZB X NZW)F1 mice exhibit a lupus-like disease (elevated levels of IgG antinuclear antibodies and a fatal glomerulonephritis) that is not characteristic of either parent. At least three gene loci have been identified in NZW mice that could potentially contribute to a T cell-dependent autoimmune disease, including the T cell receptor alpha- and beta-chain gene complexes and the major histocompatibility complex (MHC). The NZW T cell receptor beta-chain complex appeared to be particularly unusual in that the C beta 1, D beta 2, and J beta 2 gene segments have been deleted. However, an analysis of (NZB X NZW)F1 X NZB back-cross mice revealed no association of disease expression with the presence of this allele. There was also no correlation of disease incidence with the presence of the NZW T cell receptor alpha-chain allele. In contrast, nearly 90% of the backcross mice with the NZW MHC expressed severe autoimmune disease compared with 12% of the mice that did not carry this haplotype. Additional studies strongly suggested that the gene(s) within the NZW MHC is the only dominant NZW genetic contribution to F1 disease. We also determined if self-reactive T cells are able to escape thymic tolerance in autoimmune New Zealand and MRLlpr/lpr mice. In nonautoimmune mice expressing I-E, T cells utilizing V beta 17a and V beta 11 encoded domains have been shown to be clonally eliminated in the thymus. Similarly, V beta 8.1+ and V beta 6+ T cells are tolerized in nonautoimmune mice expressing Mls-1a. These T cell subsets were quantified in the lymph nodes and spleens of (NZB X NZW)F1, (NZB X SWR)F1, and MRL-lpr/lpr mice before and after the development of lupus-like disease. The results indicate that peripheral T cells in these mice, including the massive CD4-, CD8- T cell population in lpr mice, have been modified by normal mechanisms of tolerance such that potential self-reactive V beta specificities have been eliminated in the thymus.

Structure and evolution of mouse interleukin 6 gene

Restriction fragment length polymorphism in the interleukin 6 gene of murine rodents extending phylogenetically from Mus musculus domesticus to the rat has been analyzed. Most species exhibit distinct restriction site patterns. In contrast, limited polymorphism was found in the tumor necrosis factor alpha gene indicating different selective pressure acting on both genes. The gene encoding interleukin 6 was isolated from a genomic library and the exon/intron organization was determined by restriction analysis and limited DNA sequence analysis. It consists of five exons which distribute over about seven kilobases, thus resembling in structure and organization the human counterpart. Furthermore, no restriction fragment length polymorphisms in the interleukin 6 gene of autoimmune strains NZB, NZW, MRL-lpr/lpr and BxSB could be detected for either EcoRI, BamHI or HindIII.

Genetic analysis of the imperfect association of H-2 haplotype with lupus-like autoimmune disease

Unlike parental New Zealand Black (NZB) or New Zealand White (NZW) mice, (NZB x NZW)F1 mice exhibit a lupus-like disease characterized by high serum levels of IgG anti-nuclear antibodies and a fatal immune complex glomerulonephritis. Previous results from studying [(NZB x NZW)F1 x NZB] backcross mice indicated that the NZW major histocompatibility complex (MHC) or gene(s) closely linked to this locus provides the major dominant NZW genetic contribution to the F1 disease. A surprising feature of the results was the 12% frequency of discordance between the autoimmune phenotype and the presence of the NZW H-2z haplotype. In the current study, we attempted to precisely define the position of the NZW gene(s) required for lupus-like renal disease by mapping genes in individual backcross mice that are both centromeric and telomeric to the MHC and then correlating genotypes for each locus with disease. The data indicate that an adjacent NZW locus does not provide a more accurate correlation with the autoimmune phenotype compared with MHC genes themselves. Thus, the imperfect association of MHC haplotype with disease in this murine model is not explained by genetic recombination with linked genes. These data may provide insight into the mechanisms by which MHC antigens increase the probability of developing autoimmune disease and may help explain the difficulty of defining MHC relationships in human systemic lupus erythematosus.

Analysis of restriction fragment length polymorphism in lymphokine genes of normal and autoimmune mice

Analysis of RFLP has been employed in lymphokine genes of autoimmune and normal mice. No polymorphism could be detected in the loci containing IL-2, IL-2 receptor, IL-5, and IFN-gamma in NZB, NZW, BxSB, and MRL/lpr mice when compared with normal mice. Allelic forms were identified in the IL-1 alpha gene of BALB/c and in the IL-4 gene of NZW. The frequency of the Bam HI RFLP in the TNF-alpha gene of NZW which has been proposed to be associated with the development of autoimmune disease in (NZB x NZW)F1 mice has been analyzed in a number of different inbred strains and in wild mice. Since the same allele is inherited in most autoimmune, healthy laboratory and wild mice the TNF-alpha gene does not seem to be one of the causal agents that contributes to the development of autoimmunity in (NZB x NZW)F1 mice.