The contribution of L3T4+ T cells to lymphoproliferation and autoantibody production in MRL-lpr/lpr mice

Crucial role of donor-derived stromal cells in successful treatment for intractable autoimmune diseases in mrl/lpr mice by bmt via portal vein

We have recently established a new bone marrow transplantation (BMT) method for the treatment of intractable autoimmune diseases in MRL/lpr mice; the method consists of fractionated irradiation (5.5 Gy x 2), followed by BMT of whole bone marrow cells (BMCs) from allogeneic C57BL/6 mice via the portal vein (abbreviated as 5.5 Gy x 2 + PV). In the present study, we investigate the mechanisms underlying the early engraftment of donor-derived cells in MRL/lpr mice by this method. In the mice treated with this method, the number of donor-derived cells possessing the mature lineage (Lin) markers rapidly increased in the BM, spleen, and liver; almost 100% were donor-derived cells by 14 days after the treatment. The number of donor-derived hemopoietic progenitor cells (defined as c-kit(+)/Lin(-) cells) increased in the BMCs, hepatic mononuclear cells, and especially spleen cells by 14 days after the treatment. Simultaneously, hemopoietic foci adjoining donor-derived stromal cells were observed in the liver when injected via the PV, but not via the peripheral vein (i.v.). When adherent cell-depleted BMCs were injected via the PV, recipients showed a marked reduction in the survival rate. However, when mice were transplanted with adherent cell-depleted BMCs with cultured stromal cells, all the recipients survived. These findings suggest that not only donor hematopoietic stem cells (HSCs) but also donor stromal cells administered via the PV were trapped in the liver, resulting in the early engraftment of donor HSCs in cooperation with donor-derived stromal cells. This new strategy to facilitate the early recovery of hemopoiesis would therefore be of great advantage in human application.

Lupus nephritis: lessons from experimental animal models

Lupus nephritis is a frequent and severe complication of SLE. In the last decades, animal models for SLE have been studied widely to investigate the immunopathology of this autoimmune disease because abnormalities can be studied and manipulated before clinical signs of the disease become apparent. In this review an overview is given of our current knowledge on the development of lupus nephritis, as derived from animal models, and a hypothetical pathway for the development of lupus nephritis is postulated. The relevance of the studies in experimental models in relationship with our knowledge of human SLE is discussed.

Alleviation of renal disease and lymphadenopathy in MRL-Fasp(lrcg)/Fas(lprcg) (MR-lpr(cg)) mice neonatally infected with mouse mammary tumor virus encoding superantigen strongly reactive with TCR Vbeta8.2 element

Mouse mammary tumor virus transmitted by FM mice (FM-MMTV) encodes a superantigen (SAg) characterized by strong reactivity with TCR Vbeta8.2 element and broad spectrum of Vbeta reactivity. To investigate what effects the expression in vivo of FM-MMTV SAg exhibits on the course of the disease in a lupus-prone model, MRL/MpJ-Fas(lprcg)/Fas(lprcg) (MRL-lpr9cg) mice, neonatally FM-MMTV-infected MRL-lprcg(MMTV) and uninfected MRL-lpr(cg) mice were compared for various disease parameters. In MRL-lprcg(MMTV), survival was significantly prolonged, glomerulonephritis, proteinuria, and lymphadenopathy were clearly ameliorated, and the production of serum immunoglobulin G (IgG), complement-activating IgG2a, and cryogenic IgG3 autoantibodies, which are thought to be pathogenic to kidneys, and circulating immune complexes (IC), and glomerular IC deposition were significantly suppressed. FM-MMTV infection deleted Vbeta8.2+ cells by about 90% and Vbeta14+ cells less efficiently in all of the CD4+, CD8+, and B220+ CD4- CD8- or double-negative (DN) T-cell populations, and Vbeta8.1+ cells in the CD4+ population but not in the others. Similar deletion profiles of CD8+ and DN T cells support that DN T cells are derived from the CD8 lineage. The results imply that the specific regulation of the immune system with viral SAg has a potential for development of an attractive immunomodulatory therapy of autoimmune diseases.

T cell studies in a peptide-induced model of systemic lupus erythematosus

We have previously reported that immunization with a peptide mimetope of dsDNA on a branched polylysine backbone (DWEYSVWLSN-MAP) induces a systemic lupus erythematosus-like syndrome in the nonautoimmune BALB/c mouse strain. To understand the mechanism underlying this breakdown in self tolerance, we examined the role of T cells in the response. Our results show that the anti-foreign and anti-self response induced by immunization is T cell dependent and is mediated by I-E(d)-restricted CD4(+) T cells of the Th1 subset. In addition, generation of the critical T cell epitope requires processing by APCs and depends on the presence of both DWEYSVWLSN and the MAP backbone. The breakdown in self tolerance does not occur through cross-reactivity between the T cell epitope of DWEYSVWLSN-MAP and epitopes derived from nuclear Ags. In this induced-model of SLE, therefore, autoreactivity results from the activation of T cells specific for foreign Ag and of cross-reactive anti-foreign, anti-self B cells. Despite the fact that tissue injury is mediated by Ab, the critical initiating T cell response is Th1.

A pivotal role of cell-bound but not soluble CD4 molecules in full development of lupus-like manifestations in MRL-Fas(lprcg)/Fas(lprcg) mice

The role of CD4 molecules in the autoimmune and lymphoproliferative syndrome caused by murine Fas mutations was studied using the novel systemic lupus erythematosus (SLE) model, MRL-Fas(lpr(cg))/Fas(lprcg) (MRL-lpr(cg)) mice, in combination with the novel mutant CD4 gene producing soluble CD4 (sCD4) instead of membrane-bound CD4 (mCD4). For this purpose, various autoimmune manifestations were compared among MRL-lpr(cg) mice homozygous (CD4slprcg), heterozygous (CD4s/mlpr(cg)), and wild-type (CD4mlpr(cg)) for the CD4 mutation. The mortality, glomerulonephritis, proteinuria, and lymphadenopathy were significantly ameliorated in CD4slprcg compared with CD4mlpr(cg) and CD4s/mlpr(cg) mice, both being comparable in these clinical characteristics. In parallel with the clinical improvement, the serum levels of immunoglobulin, anti-DNA antibodies, anti-nuclear antibodies and immune complexes, and the extent of glomerular immune deposition, were significantly lower in the former. The results indicate that mCD4 is important and can not be replaced by sCD4 in full development of SLE-like manifestations, and suggest that CD4+ T cells may aggravate the autoimmune disease by stimulating autoreactive B cells to produce autoantibodies through their helper activity in Fas mutant models. The sCD4 levels in the serum and spleen elevated with the increased accumulation of B220+CD4-CD8- (double-negative (DN)) T cells in CD4slpr(cg) mice. This, together with the significantly milder lymphadenopathy associated with lower DN T cell contents in CD4slpr(cg) than CD4mlpr(cg) mice, implies that some of abnormal DN T cells may be derived from cells of the CD4 lineage.

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.

CTLA4IgG gene delivery prevents autoantibody production and lupus nephritis in MRL/lpr mice

MRL/MP-lpr/lpr (MRL/lpr) mice spontaneously develop an autoimmune syndrome closely resembling systemic lupus erythematosus (SLE) in humans, characterized by hypergammaglobulinemia, various autoantibody production, and the development of fatal glomerulonephritis. We have previously demonstrated that systemic administration of soluble form of CTLA4IgG prevented autoantibody-related diseases in MRL/lpr mice. To test the potential protective effects of CTLA4IgG gene delivery on the development of lupus nephritis, we injected MRL/lpr mice with a recombinant adenovirus vector containing CTLA4IgG gene, Adex1CACTLA4IgG (AdCTLA4IgG). It was demonstrated that a single administration of intravenous injection of AdCTLA4IgG into MRL/lpr mice resulted in almost complete amelioration of lupus nephritis.

Treatment of intractable autoimmune diseases in MRL/lpr mice using a new strategy for allogeneic bone marrow transplantation

A new bone marrow transplantation (BMT) method for treating severe autoimmune diseases in chimeric resistant MRL/lpr mice is presented. The method consists of fractionated irradiation (5.5 Gy × 2), followed by portal venous (PV) injection of whole bone marrow cells (BMCs) from allogeneic normal C57BL/6 (B6) mice and intravenous (IV) injection of whole B6 BMCs 5 days after the PV injection (abbreviated as 5.5 Gy × 2 + PV + IV). All recipients survived more than 1 year after this treatment (more than 64 weeks after birth). Abnormal T cells (Thy1.2+/B220+/CD3+/CD4−/CD8−) present in MRL/lpr mice before the treatment disappear, and hematolymphoid cells are reconstituted with donor-derived cells. The treated mice are free from autoimmune diseases. Levels of autoantibodies (IgG/IgM anti-ssDNA antibodies and IgG/IgM rheumatoid factors) decrease to normal levels. Successful cooperation is achieved among T cells, B cells, and antigen-presenting cells (APCs) of the treated MRL/lpr mice when evaluated by in vitro anti-SRBC responses. Newly developed T cells are tolerant to both donor (B6)-type and host (MRL/lpr)-type major histocompatibility complex (MHC) determinants. These findings clearly indicate that severe autoimmune diseases in MRL/lpr mice are completely ameliorated by the treatment without recourse to immunosuppressants, and that the treated MRL/lpr mice show normal immune functions, strongly suggesting that this strategy would be applicable to humans.

Tumor necrosis factor sustains the generalized lymphoproliferative disorder (gld) phenotype

Tumor necrosis factor (TNF) and Fas ligand (FasL) play major roles in the homeostasis of the peripheral immune system. This becomes dramatically obvious in the absence of a functional FasL. Mice with such a deficiency develop a profound lymphadenopathy, splenomegaly, hypergammaglobulinemia, and strain-dependent systemic autoimmune disease, and succumb to premature death. It is consequently termed generalized lymphoproliferative disorder (gld). By contrast, TNF deficiency alone does not result in a striking phenotype. Thus, we sought to determine what role TNF might play in contributing to the gld phenotype by creating C57BL/6.gld.TNF(-/-) mice. Contrary to the expected outcome, mice deficient for both FasL and TNF had a substantially milder gld phenotype with regard to mortality, lymphoaccumulation, germinal center formation, and hypergammaglobulinemia. To confirm these data in a strain highly permissive for the phenotype, C3H/HeJ.gld and C3H.HeJ.lpr mice were treated with a TNF-specific monoclonal antibody. This transient neutralization of TNF also resulted in a significantly attenuated lymphoproliferative phenotype. We conclude that TNF is necessary for the full manifestation of the lymphoproliferative disorder, in particular playing a critical role in lymphoaccumulation. Most importantly, absence of TNF protects gld mice against premature death.

Monocyte chemoattractant protein 1-dependent leukocytic infiltrates are responsible for autoimmune disease in MRL-Fas(lpr) mice

Infiltrating leukocytes may be responsible for autoimmune disease. We hypothesized that the chemokine monocyte chemoattractant protein (MCP)-1 recruits macrophages and T cells into tissues that, in turn, are required for autoimmune disease. Using the MRL-Fas(lpr) strain with spontaneous, fatal autoimmune disease, we constructed MCP-1-deficient MRL-Fas(lpr) mice. In MCP-1-intact MRL-Fas(lpr) mice, macrophages and T cells accumulate at sites (kidney tubules, glomeruli, pulmonary bronchioli, lymph nodes) in proportion to MCP-1 expression. Deleting MCP-1 dramatically reduces macrophage and T cell recruitment but not proliferation, protects from kidney, lung, skin, and lymph node pathology, reduces proteinuria, and prolongs survival. Notably, serum immunoglobulin (Ig) isotypes and kidney Ig/C3 deposits are not diminished in MCP-1-deficient MRL-Fas(lpr) mice, highlighting the requirement for MCP-1-dependent leukocyte recruitment to initiate autoimmune disease. However, MCP-1-deficient mice are not completely protected from leukocytic invasion. T cells surrounding vessels with meager MCP-1 expression remain. In addition, downstream effector cytokines/chemokines are decreased in MCP-1-deficient mice, perhaps reflecting a reduction of cytokine-expressing leukocytes. Thus, MCP-1 promotes MRL-Fas(lpr) autoimmune disease through macrophage and T cell recruitment, amplified by increasing local cytokines/chemokines. We suggest that MCP-1 is a principal therapeutic target with which to combat autoimmune diseases.

IL-12 Drives IFN-γ-Dependent Autoimmune Kidney Disease in MRL-Fas lpr Mice

IL-12 is secreted by kidney tubular epithelial cells in autoimmune MRL-Faslpr mice before renal injury and increases with advancing disease. Because IL-12 is a potent inducer of IFN-γ, the purpose of this study was to determine whether local provision of IL-12 elicits IFN-γ-secreting T cells within the kidney, which, in turn, incites injury in MRL-Faslpr mice. We used an ex vivo retroviral gene transfer strategy to construct IL-12-secreting MRL-Faslpr tubular epithelial cells (IL-12 “carrier cells”), which were implanted under the kidney capsule of MRL-Faslpr mice before renal disease for a sustained period (28 days). IL-12 “carrier cells” generated intrarenal and systemic IL-12. IL-12 fostered a marked, well-demarcated accumulation of CD4, CD8, and double negative (CD4−CD8− B220+) T cells adjacent to the implant site. We detected more IFN-γ-producing T cells (CD4 > CD8 > CD4−CD8− B220+) at 28 days (73 ± 14%) as compared with 7 days (20 ± 8%) after implanting the IL-12 “carrier cells;” the majority of these cells were proliferating (60–70%). By comparison, an increase in systemic IL-12 resulted in a diffuse acceleration of pathology in the contralateral (unimplanted) kidney. IFN-γ was required for IL-12-incited renal injury, because IL-12 “carrier cells” failed to elicit injury in MRL-Faslpr kidneys genetically deficient in IFN-γ receptors. Furthermore, IFN-γ “carrier cells” elicited kidney injury in wild-type MRL-Faslpr mice. Taken together, IL-12 elicits autoimmune injury by fostering the accumulation of IFN-γ-secreting CD4, CD8, and CD4−CD8− B220+ T cells within the kidney, which, in turn, promote a cascade of events culminating in autoimmune kidney disease in MRL-Faslpr mice.

The effect on immunoglobulin glycosylation of altering in vivo production of immunoglobulin G

The effect on murine immunoglobulin G (IgG) glycosylation of altering IgG production in vivo was assessed in interleukin (IL)-6 transgenic and CD4 knockout mice. C57BL/6 mice carrying the IL-6 transgene showed increased levels of circulating IgG. This was associated with decreased levels of galactose on the IgG oligosaccharides. No decrease in beta4-galactosyltransferase mRNA or in enzyme activity was seen in IL-6 transgenic mice. MRL-lpr/lpr mice normally have elevated levels of circulating IgG, again accompanied by decreased levels of IgG galactose. Disruption of the CD4 gene in MRL-lpr/lpr mice led to a substantial decrease in the concentration of circulating IgG, but IgG galactose levels remained low. Thus, an enforced decrease in IgG levels in the lymphoproliferative MRL-lpr/lpr mice did not alter the percentage of agalactosyl IgG in these mice, suggesting that agalactosyl IgG production is not simply caused by excessive IgG synthesis leading to an insufficient transit time in the trans-Golgi, but rather to a molecular defect in the interaction between galactosyltransferase and the immunoglobulin heavy chain.

Efficacy of a pure compound H1-A extracted from Cordyceps sinensis on autoimmune disease of MRL lpr/lpr mice

Cordyceps sinensis (CS) is a traditional Chinese medicine with immunomodulatory effect and is effective in improving the survival of lupus mice. In the present study we isolated a pure compound (H1-A) from CS and investigated its effect on inhibiting autoimmune disease progression in MRL Ipr/Ipr mice. Our results demonstrated that MRL Ipr/Ipr mice treated daily with H1-A (40 microg/kg/d orally) for 8 weeks had a progressive reduction in anti-ds-DNA production (optical density value decreased from 0.172 +/- 0.009 to 0.112 +/- 0.015) when compared with the control group (optical density value increased from 0.141 +/- 0.036 to 0.198 +/- 0.047). In clinical presentation, the treated group had a reduction in lymphadenopathy, a delayed progression of proteinuria, and an improvement in kidney function. Histologic analysis of kidney tissue indicated that H 1-A could inhibit the mesangial proliferation that was evident in lupus nephritis. However, there was no significant change in immune complex deposition. The studies reveal that the pure compound (H1-A) may be potentially useful for treating systemic lupus erythematosus in human patients, and they provide some questions for further investigation of the pathogenesis of systemic lupus erythematosus and lupus nephritis.

Autoreactive T cells in murine lupus: origins and roles in autoantibody production

The conventional paradigm to explain systemic lupus erythematosus (SLE) is that disease results from tissue deposition of pathogenic autoantibodies and immune complexes, secondary to activation of autoreactive B cells in the context of help from alphabeta T cells. Recent work in murine lupus has confirmed this notion and demonstrated that autoantigen-specific alphabeta T cells are absolutely required for full penetrance of disease, with such autoreactive alphabeta T cells, even in Fas-intact mice, likely arising from defects in peripheral tolerance. These studies have also revealed a network of regulation that also involves nonclassical pathogenic and downregulatory alphabeta and gammadelta T cells, suggesting that the lupus immune system involves more complex interactions than the conventional paradigm suggests.

Death and destruction of activated T lymphocytes

The massive clonal expansion that occurs during an antigen-specific immune response results in the flooding of immune organs with activated T lymphocytes. At the end of a specific response, the vast majority of these activated T cells are cleared from the immune system. The T cells receive signals through specific death receptors that are expressed as a result of activation. Death receptors transmit their apoptotic signals through the activation of caspases. Function of the death receptors is intimately linked to cell-cycle control, and many cell-cycle control proteins are caspase substrates. Among CD8+ T cells, apoptotic death occurs at a specific site, the sinusoids of the liver. The liver appears to contain a mechanism for the trapping and killing of activated T cells, rendering it an immunologically privileged site.

Role of the Costimulatory Molecule CD28 in the Development of Lupus in MRL/lpr Mice

MRL/Mpj-lpr/lpr (MRL/lpr) mice develop autoimmune disorders, including lymphoproliferation, glomerulonephritis, autoantibody production, and hypergammaglobulinemia. To investigate the role of the costimulatory molecule CD28 in the development of these disorders, MRL/lpr mice lacking CD28 were generated by gene targeting. Compared with CD28+/+ MRL/lpr mice, CD28−/− MRL/lpr mice showed decreased lymphadenopathy but increased splenomegaly associated with the expansion of abnormal B220+ TCRαβ+ T cells. Although levels of IgM Abs were unchanged in CD28−/− MRL/lpr mice, the production of anti-DNA IgG Abs and IgG rheumatoid factors were suppressed. IgG deposition in the glomeruli was markedly decreased, and the development of glomerulonephritis was significantly retarded. Furthermore, renal vasculitis and arthritis were absent in CD28−/− MRL/lpr mice. These results indicate that, although CD28 is not required for the generation of the abnormal T cell population in MRL/lpr mice, it does play an important role in the development of autoimmune disease in these animals.

B7 Costimulation in the Development of Lupus: Autoimmunity Arises Either in the Absence of B7.1/B7.2 or in the Presence of Anti-B7.1/B7.2 Blocking Antibodies

Costimulatory molecules, termed B7.1 and B7.2, are present on the surfaces of APC and are important for the activation of T lymphocytes specific for both foreign Ags and autoantigens. We have examined the role of B7 costimulation in the MRL-lpr/lpr murine model of human systemic lupus erythematosus. MRL-lpr/lpr mice receiving both anti-B7.1 and anti-B7.2 Abs expressed significantly lower anti-small nuclear ribonucleoprotein particles (snRNP) and anti-dsDNA autoantibodies than did untreated mice. Anti-B7.2 Ab treatment alone inhibited anti-dsDNA autoantibody expression while having no effect on anti-snRNP autoantibody expression. Anti-B7.1 Ab treatment alone did not change the expression of either anti-snRNP or anti-dsDNA autoantibodies. Parallel studies performed in MRL-lpr/lpr mice genetically deficient in either B7.1 or B7.2 expressed autoantibody profiles comparable to those found in wild-type MRL-lpr/lpr mice. However, B7.1-deficient MRL-lpr/lpr mice exhibited distinct and more severe glomerulonephritis while B7.2-deficient MRL-lpr/lpr mice had significantly milder or absent kidney pathology as compared with age-matched wild-type mice. These studies indicate that each B7 costimulatory signal may control unique pathological events in murine systemic lupus erythematosus that may not always be apparent in autoantibody titers alone.

Isoaspartyl post-translational modification triggers autoimmune responses to self-proteins

The normal functioning immune system is programmed to attack foreign pathogens and other foreign proteins while maintaining tolerance to self-proteins. The mechanisms by which tolerance is broken in the initiation of autoimmunity are not completely understood. In the present study, mice immunized with the murine cytochrome c peptide 90-104 showed no response by the B or T cell compartments. However, immunization with the isoaspartyl form of this peptide, where the linkage of Asp(93) to Leu(94) occurs through the beta-carboxyl group, resulted in strong B and T cell autoimmune responses. Antibodies elicited by immunization with the isoaspartyl form of self-peptide were cross-reactive in binding to both isoforms of cytochrome c peptide and to native cytochrome c self-protein. In a similar manner, immunization of mice with the isoaspartyl form of a peptide autoantigen of human systemic lupus erythematosus (SLE) resulted in strong B and T cell responses while mice maintained tolerance to the normal aspartyl form of self-antigen. Isoaspartyl linkages within proteins are enhanced in aging and stressed cells and arise under physiological conditions. These post-translationally modified peptides may serve as an early immunologic stimulus in autoimmune disease.

Cellular Immunity to β2-Glycoprotein-1 in Patients with the Antiphospholipid Syndrome

Patients with antiphospholipid syndrome (APS) suffer recurrent thromboses, thrombocytopenia, and/or fetal loss in association with Abs that can be detected in phospholipid-dependent assays. Despite the name, the Igs associated with APS are predominantly directed against epitopes on phospholipid-binding plasma proteins, such as β2-glycoprotein-1 (β2GP1) and prothrombin. The aim of this study was to examine the cellular immune response to β2GP1 in patients with APS. Using a serum-free stimulation assay, PBMCs from 8 of 18 patients with APS proliferated to purified β2GP1 or to the β2GP1 present in serum, whereas no stimulation was observed by PBMCs from healthy individuals, patients with other autoimmune diseases, or anticardiolipin Ab-positive patients without histories of thromboses or fetal loss. The immune response was Ag-specific, requiring class II molecules, CD4+ T cells, and APCs, and was associated with a selective expansion of CD4+ but not CD8+ T cells. The proliferating T cells produced IFN-γ but not IL-4, indicating a bias toward a type 1 immune response. Chronic low grade stimulation of autoreactive β2GP1-specific, IFN-γ-producing Th1 CD4+ T cells may contribute to the high risk of thromboses and pregnancy failure in patients with APS.

Opportunities for future biological therapy in SLE

The development of monoclonal antibodies and the emergence of recombinant DNA technology has made it possible to identify and selectively inhibit distinct cell subsets, surface molecules and secreted products that contribute to normal and pathological immune responses. These advances have helped to clarify the mechanisms that promote autoimmune diseases. As a result, it is now possible to contemplate rational strategies for the treatment of these diseases. Some of these strategies are designed to influence the cell surface interactions that determine whether potentially autoreactive T cells become activated or tolerant following antigen stimulation. Other strategies are designed to augment or inhibit distinct cytokines that regulate autoimmunity. All of these strategies have shown promise in animal models for systemic lupus erythematosus, and they may soon be translated into effective new therapies for people.

Anti-CD40L Accelerates Renal Disease and Adenopathy in MRL-lpr Mice in Parallel with Decreased Thymocyte Apoptosis

The CD40/CD40L (CD40 ligand) axis regulates several interactions between T cells and B cells. Blocking of CD40 engagement by CD40L inhibits Ig class switch by B cells as well as diminishes T cell response to an immunizing Ag. For these reasons, disruption of CD40/CD40L interactions by anti-CD40L administration or by genetic disruption of CD40L has ameliorated a variety of autoimmune conditions. More recent findings suggest that a direct signal can be transmitted to T cells via their expressed CD40L, which can costimulate proliferation with CD3 or promote germinal center formation. It is therefore possible that treatment with anti-CD40L Ab might produce a different outcome than observed in genetically CD40L-deficient mice. In this regard, we observe that in contrast to the genetic deletion of CD40L in MRL-lpr mice, which diminishes autoimmune disease but has little effect on adenopathy, administration of anti-CD40L to MRL-lpr mice accelerates both of these parameters. This difference appears to result from anti-CD40L actively delivering a signal that inhibits T cell apoptosis in lpr mice. This was confirmed by in vitro studies demonstrating that CD40L cross-linking on lpr thymocytes inhibited apoptosis and surface TCR down-modulation induced by CD3 ligation.

Exogenous dehydroepiandrosterone modified the expression of T helper-related cytokines in NZB/NZW F1 mice

The onset of lupus-like disease in NZB/NZW F1 mice was correlated with the expression of IL-10 at 4 m of age, and with a sequential enhanced expression of IFN-gamma and IL-6 between 6 to 8 m of age. The expression of IFN-gamma and IL-6 was associated with exacerbation of disease symptom, production of anti-DNA antibody, and increase in total serum IgG1. Exogenous dehydroepiandrosterone (DHEA) given in animal diet significantly prolonged survival, and delayed formation of autoantibody of NZB/NZW F1 mice as compared to mice fed on control diet. The effect of DHEA paralleled a delay in the expression of IL-10 and IL-6 and an earlier detection of IL-12 transcripts. Moreover, DHEA-fed mice had higher serum IgG2a level than control diet-fed mice. Collectively, DHEA may modify the activation of distinct subset of T helper cells in NZB/NZW F1 mice at different phases of disease progression.

A New Strategy for Treatment of Autoimmune Diseases in Chimeric Resistant MRL/lpr Mice

A new strategy for the treatment of autoimmune diseases in chimeric resistant MRL/lpr mice is established. The strategy includes injection of cyclophosphamide (CY), fractionated irradiation (5 Gy × 2), bone grafts (to recruit stromal cells), and two transplantations of whole bone marrow cells (WBMCs) from allogeneic normal C57BL/6 mice (CY/2X/Bone/2BMT). MRL/lpr mice, thus treated, survived more than 40 weeks (1 mouse survived for >40 weeks, 7 for >50 weeks, and 4 for >60 weeks after these treatments). Immunohistological studies showed that the mice were completely free from both lymphadenopathy and autoimmune diseases such as systemic lupus erythematosis and rheumatoid arthritis. The levels of autoantibodies (IgM/IgG rheumatoid factors and IgM/IgG anti-ssDNA antibodies [Abs]) in the treated mice decreased to those in the normal mice. In addition, successful cooperation among T cells, B cells, and antigen-presenting cells (APCs) was observed. Abnormal T cells with immunophenotypes of B220+/Thy-1+/CD3+/CD4−/CD8−present in untreated MRL/lpr mice disappeared, and the hematolymphoid cells of the treated mice were of donor origin. However, the mice that had been irradiated with 8.5 Gy and then reconstituted with T-cell–depleted BMCs plus bone grafts died within 2 weeks due to the side effect of irradiation. The depletion of CD8+ cells (not CD4+ cells) from WBMCs resulted in graft failure; 60% of the recipient mice, thus treated, died within 2 weeks, and all recipients died by 15 weeks. Furthermore, limiting dilution assays showed that approximately more than 0.5% of T cells contained in the BMCs are necessary not only for engraftment of BMCs but also for long-term disease-free survival of the recipients. In contrast, recipients that had received CD4-depleted BMCs with CY plus fractionated irradiation (5Gy × 2) survived for more than 40 weeks without showing graft-versus-host reaction (GVHR). This indicates that CD8+cells in the BMCs are essential for the successful engraftment of the donor-type hematolymphoid cells.

A New Strategy for Treatment of Autoimmune Diseases in Chimeric Resistant MRL/lpr Mice

A new strategy for the treatment of autoimmune diseases in chimeric resistant MRL/lpr mice is established. The strategy includes injection of cyclophosphamide (CY), fractionated irradiation (5 Gy × 2), bone grafts (to recruit stromal cells), and two transplantations of whole bone marrow cells (WBMCs) from allogeneic normal C57BL/6 mice (CY/2X/Bone/2BMT). MRL/lpr mice, thus treated, survived more than 40 weeks (1 mouse survived for >40 weeks, 7 for >50 weeks, and 4 for >60 weeks after these treatments). Immunohistological studies showed that the mice were completely free from both lymphadenopathy and autoimmune diseases such as systemic lupus erythematosis and rheumatoid arthritis. The levels of autoantibodies (IgM/IgG rheumatoid factors and IgM/IgG anti-ssDNA antibodies [Abs]) in the treated mice decreased to those in the normal mice. In addition, successful cooperation among T cells, B cells, and antigen-presenting cells (APCs) was observed. Abnormal T cells with immunophenotypes of B220+/Thy-1+/CD3+/CD4−/CD8−present in untreated MRL/lpr mice disappeared, and the hematolymphoid cells of the treated mice were of donor origin. However, the mice that had been irradiated with 8.5 Gy and then reconstituted with T-cell–depleted BMCs plus bone grafts died within 2 weeks due to the side effect of irradiation. The depletion of CD8+ cells (not CD4+ cells) from WBMCs resulted in graft failure; 60% of the recipient mice, thus treated, died within 2 weeks, and all recipients died by 15 weeks. Furthermore, limiting dilution assays showed that approximately more than 0.5% of T cells contained in the BMCs are necessary not only for engraftment of BMCs but also for long-term disease-free survival of the recipients. In contrast, recipients that had received CD4-depleted BMCs with CY plus fractionated irradiation (5Gy × 2) survived for more than 40 weeks without showing graft-versus-host reaction (GVHR). This indicates that CD8+cells in the BMCs are essential for the successful engraftment of the donor-type hematolymphoid cells.

Anti-T-cell receptor therapy in murine experimental systemic lupus erythematosus

Experimental systemic lupus erythematosus (SLE), similar to that observed after immunization with the human anti-DNA mAb 16/6 Id+, could be induced in mice by injection of 16/6 Id specific T-cell lines. The above T-cell lines were exclusively CD4+ CD8- and the majority of cells expressed the Vbeta8 T-cell receptor (TCR) gene products. Furthermore, lymph node cells of mice immunized with the 16/6 Id were enriched with CD4+ Vbeta8+ T-cells. The TCR used by 16/6 Id-specific T-cells showed a limited homology in their CDR3 junctional regions. Nevertheless, mice injected with the anti-Vbeta8 mAb developed autoantibody titers that were not significantly different from those found in the non-treated, 16/6 Id-injected group.

Enhanced lymphoproliferation and diminished autoimmunity in CD4-deficient MRL/lpr mice

MRL/lpr mice spontaneously develop an autoimmune disease with features of systemic lupus erythematosus. They also develop a lymphoproliferative disorder characterized by a massive accumulation of double-negative (DN) T cells that lack both CD4 and CD8. To clarify the role of CD4 in autoimmunity and lymphoproliferation in these mice, CD4-deficient MRL/lpr mice were generated. CD4-deficient MRL/lpr mice developed massive expansion of DN T cells in the blood, spleen, and lymph nodes, which significantly exceeded the degree of lymphoproliferation in CD4-expressing control MRL/lpr mice. Despite this lymphoproliferation, CD4-deficient MRL/lpr mice produced little, if any, antibodies to double-stranded DNA, and they had prolonged survival relative to CD4-expressing littermates. However, they eventually developed moderately severe nephritis, characterized by immunoglobulin and complement deposition in glomeruli, vasculitis, and renal infiltration by CD8+ T cells. These findings indicate that (1) lymphoproliferation in MRL/lpr mice does not require the expression of CD4; (2) autoantibody production in MRL/lpr mice is dependent on the expression of CD4 and not on the accumulation of DN T cells; and (3) the development of nephritis in MRL/lpr mice involves both CD4-dependent and CD4-independent mechanisms.

Influence of microbial stimulation on hypergammaglobulinemia and autoantibody production in pristane-induced lupus

Pristane induces a lupus-like syndrome characterized by autoantibody production and glomerulonephritis in nonautoimmune strains of mice. Although it has been suggested that this syndrome results from nonspecific immune activation, there is little evidence so far that B cells are activated nonspecifically by pristane or that this promotes autoimmunity. In this study, we examined whether polyclonal hypergammaglobulinemia occurs in pristane-induced lupus, and its relationship to the production of anti-DNA, nRNP/Sm, and Su autoantibodies. In conventionally housed mice, there was a marked increase in total IgM and IgG3 2 weeks after i.p. pristane injection, followed by increased IgG1, IgG2a, and IgG2b levels. IgM levels were higher in pristane-treated specific pathogen-free (SPF) mice than in conventionally housed mice, whereas IgG and IgA levels were reduced. Pristane induced anti-nRNP/Sm and Su autoantibodies in SPF mice, but their onset was delayed and levels were lower than those in conventionally housed mice. There was no consistent relationship between total IgG1, 2a, and 2b hypergammaglobulinemia and production of anti-nRNP/Sm and Su autoantibodies. Moreover, the total Ig levels were similar in the anti-nRNP/Sm-positive and -negative groups. In contrast, production of IgM anti-ssDNA antibodies paralleled IgM hypergammaglobulinemia in some, but not all, mice. These studies indicate that pristane-induced lupus is associated with marked hypergammaglobulinemia, the magnitude of which is influenced by the microbial environment. However, anti-nRNP/Sm and Su autoantibody production is at least partly independent of polyclonal B cell activation. The data strongly suggest that pristane-induced lupus is not exclusively the consequence of nonspecific immune stimulation. They also point to the importance of microbial stimulation in the development of hypergammaglobulinemia in this inducible lupus model.

Effects of administration of monoclonal antibodies (anti-CD4 or anti-CD8) on the development of autoimmune diseases in (NZW x BXSB)F1 mice

(NZW x BXSB)F1 (W/BF1) mice spontaneously develop autoimmune diseases, characterized by lymphadenopathy, lupus nephritis, and immune thrombocytopenia associated with various autoantibodies such as anti-DNA, anti-platelet and anti-cardiolipin antibodies (Abs). In the present study, we investigate the effects of administration of monoclonal Abs (anti-CD4 or anti-CD8 mAb) on the development of autoimmune diseases in W/BF1 mice. MAb was administered from the age of 7 weeks. Prolongation of survival rate and reduction of severity of autoimmune diseases were observed after treatment with anti-CD4 mAb. However, anti-CD8 mAb treatment accelerated the diseases. Serum levels of IFN-gamma and IL-10 in old W/BF1 mice were significantly high, whereas IL-4 levels were low in comparison with those of young W/BF1 mice; the expression of mRNA of IFN-gamma, IL-4 or IL-10 in CD4+ T cells of old W/BF1 mice was parallel to the serum levels of each cytokine. These observations suggest that CD4+ cells are involved in the development of autoimmune diseases in W/BF1 mice, and that CD8+ cells have a suppressive effect on the development of autoimmune diseases in W/BF1 mice.

Mechanism of ovarian autoimmunity: induction of T cell and antibody responses by T cell epitope mimicry and epitope spreading

Autoimmune diseases are often manifested as organ inflammation with loss of function, and detectable autoreactive T cell and autoantibody responses. In the proper genetic context, we have shown that these parameters of autoimmunity can result from a single pivotal event: the induction of a strong and persistent T cell response for a foreign or unrelated self peptide that mimics the target self peptide. This may apply to organ-specific and systemic autoimmunity, independent of whether the tissue inflammation results from T cell immune mechanism or antibodies. T cell peptide mimicry, through sharing of critical residues or by a less defined mechanism, can result in autoimmune disease. Once triggered, the helper T cell response leads rapidly to a concomitant autoantibody response spreading to distant B cell determinants of the self protein antigen. Evidently, with T cell help, endogenous antigens can stimulate B cells to provoke a functional autoantibody response against conformational antigenic determinants. These findings are based on recent studies on a novel autoimmune ovarian disease model induced by a self peptide with well-defined T and B cell epitopes. However, studies reported on systemic lupus erythematosus models have shown that similar events may result in autoantibody response in systemic autoimmunity.

Perforin Protects Against Autoimmunity in Lupus-Prone Mice

The roles of cytolytic regulatory mechanisms in the immune system of lupus-prone mice were examined in perforin-deficient animals bearing functional or defective (lpr) Fas Ag (CD95). Perforin-deficient Fas+ animals developed accelerated autoimmunity, characterized by increased hypergammaglobulinemia, autoantibody production, and immune deposit-related end-organ disease compared with perforin-intact counterparts. In comparison, perforin-deficient lpr animals had accelerated mortality compared with perforin-intact lpr mice, associated with the abnormal accumulation of CD3+CD4−CD8− αβ T cells in conjunction with unaltered hypergammaglobulinemia, autoantibody production, and immune complex renal disease. These results indicate that cytolytic lymphoid regulation plays critical roles in the immune homeostasis of lupus-prone animals, and identify perforin-mediated cytotoxicity as a specific mechanism in the regulation of systemic autoimmunity.

Pathogenesis of autoimmunity in alphabeta T cell-deficient lupus-prone mice

Murine lupus in MRL mice has been strongly attributed to alphabeta T cell-dependent mechanisms. Non-alphabeta T cell-dependent mechanisms, such as gammadelta T cells, have been shown to drive antibody and autoantibody production, but they have not been considered capable of inducing end-organ disease. Here, we have expanded upon the findings of such previous work by examining the mechanism and extent of end-organ disease attainable via gammadelta T cells and/or non-alphabeta T cell-dependent mechanisms, assessing two prototypical lupus lesions, renal and skin disease, in TCR alpha -/- MRL mice that possessed either functional or defective Fas antigen (Fas + or lpr). Observed to 1 year of age, TCR alpha -/- MRL mice developed disease characterized by increased mortality, overt renal disease and skin lesions. While delayed in onset and/or reduced in severity compared with TCR alpha +/+ MRL/lpr animals, renal and skin lesions in alphabeta T cell-deficient animals were clearly increased in severity compared with age-matched control non-autoimmune mice. In contrast to TCR alpha +/+ MRL mice, whose disease reflected pan-isotype immune complex deposition with significant complement fixation, renal disease in TCR alpha -/- MRL animals reflected predominantly IgG1 immune complex deposition, with poor complement fixation. Thus, this study demonstrates conclusively that non-alphabeta T cell-dependent mechanisms can induce renal and skin injury in murine lupus, but at least in the kidney, only via humoral autoimmunity of a relatively non-pathological isotype which results in the delayed onset of end-organ damage.

Why do defects in the Fas-Fas ligand system cause autoimmunity?

We have previously isolated genes that encode Fas and Fas ligand, a receptor-ligand pair that mediates an apoptotic signal. We also have demonstrated that lpr and gld mice, well-known animal models of autoimmune disease are loss-of-function mutants of the Fas and Fas ligand genes, respectively. Patients with autoimmune lymphoproliferative disorders have been found to bear mutations of the Fas gene. These findings indicate that the Fas-Fas ligand system plays an important role in the maintenance of self-tolerance among both humans and mice. During T-cell development, mouse T cells initially express Fas in the thymus and maintain their expression thereafter. Peripheral B cells usually express Fas at much lower levels than do T cells, but various stimuli enhance Fas expression on B cells. In contrast, among the lymphocyte subsets, only activated T cells and natural killer cells express readily detectable levels of Fas ligand. Reactivation of previously activated T cells through T-cell receptors induces apoptosis. This phenomenon (activation-induced cell death) is mediated by means of the Fas-Fas ligand interaction. We recently discovered that peripheral naive T cells in mice are susceptible to Fas ligand but not to agonistic anti-Fas antibodies. To our surprise, engagement of T-cell receptors on naive T cells was shown to induce Fas ligand resistance. On the basis of these findings and other reports, we discuss how the breakdown of self-tolerance occurs as the result of defects in the Fas-Fas ligand system.

Autoantibody production and cytokine profiles of MHC class I (beta2-microglobulin) gene deleted New Zealand black (NZB) mice

We established a colony of MHC class I deleted (knockout) NZB mice, which lack the beta2 microglobulin gene (NZB.beta2m-/-), to characterize the contribution of MHC class I to the thymic microenvironment abnormalities, autoantibody production and lupus-like disease of NZB mice. Using an extensive panel of well characterized monoclonal antibodies defining thymic epithelial and other stromal elements, we demonstrated that deletion of MHC class I molecules does not change the thymic abnormalities, including the presence of a cortical epithelial cell free region, ectopic expression of medullary epithelial antigens, and the irregular shape of the medullary epithelial network of NZB mice. Moreover, the decreased staining of MTS 33(+) cells, a marker of premature thymocyte maturation, was also seen in NZB.beta2m-/-. However, although NZB.beta2m-/- mice had approximately the same levels of IgM and IgG anti-ss and dsDNA antibodies when compared to control NZB mice, there were significant alterations in the incidence and onset of anti-erythrocyte antibody levels. NZB.beta2m-/- had a lower incidence and a delayed onset of anti-erythrocyte autoantibody production compared to that seen in NZB mice. We also compared constitutive and PHA-P-driven levels of IFN-gamma, IL-4, IL-6, and IL-12 in cells from NZB, NZB.beta-/-2, and control C57BL/6 mice. Mitogen stimulated cells showed a decreased IFN-gamma, and a marked increase in IL-6 and IL-12 in NZB and NZB.beta2m-/- mice.

Roles of interferon-gamma and interleukin-4 in murine lupus

The systemic autoimmune syndrome of MRL/Mp-lpr/lpr (MRL/lpr) mice consists of severe pan-isotype hypergammaglobulinemia, autoantibody production, lymphadenopathy, and immune complex-associated end-organ disease. Its pathogenesis has been largely attributed to helper alphabeta T cells that may require critical cytokines to propagate pathogenic autoantibody production. To investigate the roles of prototypical Th1 and Th2 cytokines in the pathogenesis of murine lupus, IFN-gamma -/- and IL-4 -/- lupus-prone mice were generated by backcrossing cytokine knockout animals against MRL/lpr breeders. IFN-gamma -/- animals produced significantly reduced titers of IgG2a and IgG2b serum immunoglobulins as well as autoantibodies, but maintained comparable levels of IgG1 and IgE in comparison to cytokine-intact controls; in contrast, IL-4 -/- animals produced significantly less IgG1 and IgE serum immunoglobulins, but maintained comparable levels of IgG2a and IgG2b as well as autoantibodies in comparison to controls. Both IFN-gamma -/- and IL-4 -/- mice, however, developed significantly reduced lymphadenopathy and end-organ disease. These results suggest that IFN-gamma and IL-4 play opposing but dispensable roles in the development of lupus-associated hypergammaglobulinemia and autoantibody production; however, they both play prominent roles in the pathogenesis of murine lupus-associated tissue injury, as well as in lpr-induced lymphadenopathy.

B cells in systemic autoimmune disease: recent insights from Fas-deficient mice and men

In mice functionally deficient for either Fas or Fas ligand expression, the failure of Fas-ligand-expressing cytotoxic T cells to eliminate autoreactive B cells can result in excessive autoantibody production. Recent in vitro studies have shown that B cells activated by CD40 ligand become extremely sensitive to Fas-mediated apoptosis while IL-4 and/or surface IgM receptor engagement protects B cells from Fas ligand cytolysis. Potential in vivo sites for Fas ligand regulation of self-reactive B cells have been suggested and implications for human disease have been investigated.

Lymph node cell vaccination against the lupus syndrome of MRL/lpr/lpr mice

Immunization with pathogenic lymphoid cells has been shown to induce resistance to disease in experimental animal models of cell mediated autoimmunity. In the present work we tested the effectiveness of this approach in a spontaneous murine autoimmune disease, the MRL/lpr/lpr (MRL/1) murine lupus model. We now report that the anti-DNA antibodies and glomerulonephritis of MRL/1 mice could be prevented by the adoptive transfer of spleen cells from MRL/+ mice that had been vaccinated with MRL/1 lymph node T lymphocytes, but not by direct vaccination of MRL/1 mice with their cells. These results indicate that the lupus of MRL/1 mice is susceptible to regulation by adoptive vaccination and that these autoimmune mice lack the ability to raise a suppressive response against their own pathogenic cells.

Imbalance towards Th1 predominance is associated with acceleration of lupus-like autoimmune syndrome in MRL mice

To investigate the respective roles of Th1 and Th2 cells in the pathogenesis of lupus-like autoimmune disease, we have analyzed the spontaneous and antigen-induced productions of IgG1 vs IgG2a and IgG3 subclasses in relation to the mRNA expression of INF-gamma (Th1 cytokine promoting IgG2a and IgG3 production), IL-4 (Th2 cytokine promoting IgG1 production), and IL-10 (Th2 cytokine) in CD4+ T cells from lupus-prone MRL mice. For this purpose, two paired sets of MRL mice were chosen for the comparison of these parameters: (a) MRL-lpr/lpr (lpr for lymphoproliferation) and its recently described substrain with a prolonged survival, termed MRL-lpr/lpr.ll (ll for long lived) and (b) MRL male mice bearing the Yaa (Y-linked autoimmune acceleration) gene (MRL.Yaa) with an accelerated disease and their male counterparts lacking the Yaa gene. We demonstrate herein that the accelerated development of lupus-like autoimmune disease in MRL-lpr/lpr and MRL.Yaa mice, as compared with MRL-lpr/lpr.ll and MRL-+/+ mice, respectively, was correlated with an enhanced expression of IFN-gamma vs IL-4 and IL-10 mRNA in CD4+ T cells, which paralleled with an increase of spontaneous and foreign T cell-dependent antigen-induced productions of IgG2a and IgG3 vs IgG1 antibodies. These data suggest that an imbalance towards Th1 predominance may play a significant role in the acceleration of lupus-like autoimmune disease in MRL mice.

Thymus-dependent effects of a traditional Chinese medicine, ren-shen-yang-rong-tang (Japanese name; Ninjin-youei-to), in autoimmune MRI/MP-lpr/lpr mice

Autoimmune MRL/lpr mice were i.p. treated with 200 mg/kg Ren-shen-yang-rong-tang (Japanese name: Ninjin-youei-to, NYT), a traditional Chinese herbal medicine (Japanese name: Kampo), from 8 weeks of age every 3 days before the onset of autoimmune disease Compared to age-matched control MRL/lpr mice, the serum IL-6 concentration in NYT-treated mice was decreased, their serum IFN-gamma concentration was increased, and the proliferative responses of whole and enriched CD4+ cells in their spleen and lymph nodes stimulated with ConA in vitro were restored. FACS analysis revealed that the rate of decreased CD4+CD8+ T-cell population in the thymus was decreased in MRL/lpr mice but recovered by NYT treatment. Further, adult thymectomized (ATX) MRL/lpr mice were treated with 200 mg/kg NYT similarly. NYT treatment prolonged the survival of sham-operated MRL/lpr mice and ameliorated their proteinuria but did not improve such autoimmune manifestations in ATX-MRL/lpr mice. These findings suggest that NYT plays an important role in the abrogation of autoimmune-prone T cell differentiation and that the therapeutic effect of NYT is dependent on the thymus in MRL/lpr mice.

T cells in murine lupus: propagation and regulation of disease

MRL/Mp-lpr/lpr mice develop a spontaneous lupus syndrome, including hypergammaglobulinemia, autoantibodies, glomerulonephritis, and lymphadenopathy. To investigate the role of lymphocytes subsets in the pathogenesis of disease, lupus-prone MRL mice deficient in alpha beta T cells, gamma delta T cells, or both were generated. Mice deficient in alpha beta T cells developed a partially penetrant lupus syndrome, characterized by lymphadenopathy, elevated levels of class-switched immunoglobulins, an increased incidence of antinuclear antibodies, and immune deposits in kidneys which progressed to renal insufficiency over time. In comparison to wild type animals, gamma delta T cell-deficient animals developed an accelerated and exacerbated disease phenotype, characterized by accelerated hypergammaglobulinemia and enhanced autoantibody production and mortality. Repertoire analysis of these latter animals identified polyclonal expansion (V beta) of alpha beta CD4+ B220-cells. Mice lacking both alpha beta and gamma delta T cells failed to generate class-switched autoantibodies and immune complex renal disease. First, these findings demonstrate that murine lupus in the setting of Fas-deficiency does not absolutely require the presence of alpha beta T cells, and they also suggest that a significant basis for MRL/lpr disease, including renal disease, involves alpha beta T cell-independent, gamma delta T cell dependent, polyreactive B cell autoimmunity, upon which alpha beta T cell-dependent mechanisms aggravate specific autoimmune responses. Second, these data indicate that gamma delta T cells partake in the regulation of systemic autoimmunity, presumably via their effects on alpha beta CD4+ B220-T cells that provide B cell help. Finally, these results demonstrate that MRL/lpr B cells, despite their intrinsic abnormalities, cannot per se cause tissue injury without T cell help.

Expression of CD45-restricted form B in (NZW x BXSB) F1 and MRL/Mp-lpr/lpr mice

Expression of CD45RB on CD4+ or CD8+ cells in combination with TCRV beta usages (V beta 6, V beta 8.1, V beta 8.2, V beta 11 and V beta 17a) in normal mouse strains (BALD/c and C57BL/6) was compared with autoimmune-prone strains (NZW x BXSB) F1 and MRL/lpr) at young and old ages. The frequencies, and also the numbers of CD45RB- cells in CD4+ T cells with various TcR repertoires was significantly less in the autoimmune-prone stains at old ages, while, in normal control strains, they remained unchanged. Furthermore, CD4+/CD45RB- cells are CD44high and CD62L (L- selectin).low These findings suggest that most T cells, especially CD4+ T cells, in old W/BF1 and old MRL/lpr mice, were activated and this may reflect the elevation of autoantibodies and the progress of autoimmune status in aged autoimmune-prone mice. This will be discussed in relation to the progress of the autoimmune diseases.

Abnormal signal transduction through CD4 leads to altered tyrosine phosphorylation in T cells derived from MRL-lpr/lpr mice

CD4+ T cells play a crucial role in the development of lupus in MRL-lpr/lpr mice: incomplete deletion/silencing of self-reactive CD4+ T cells leads to T cell activation, which causes both polyclonal B cell activation and T cell infiltration of multiple organs. Furthermore, anti-CD4 antibody therapy ameliorates disease and prolongs survival. Because CD4 is normally involved in both tolerance induction and T cell activation, we questioned whether signaling through CD4 was normal among T cells in this strain. For this purpose, signal transduction in CD4+ T cells derived from MRL-lpr/lpr and normal mice were compared, using an autoreactive CD4+ T cell clone and freshly isolated CD4+ T cells derived from mice of varying ages. Tyrosine phosphorylation was similar among MRL and normal CD4+ T cells after cross-linking with either anti-TCR antibody or anti-CD3 antibody, and following co-culture with Con A. In constrast, cross-linking of surface CD4 resulted in deficient tyrosine phosphorylation of cellular proteins in MRL T cells. By comparison, lck protein expression in MRL CD4+ T cells was found to be lower than normal. However, following stimulation with Con A, lck enzyme activity, as detected by autophosphorylation of lck, was comparable in MRL and normal T cells. The observed differences were present in the autoreactive T cell clone as well as in T cells isolated from both pre-diseased and diseased mice, and they could not be explained by variation in surface density of CD4. These results raise the possibility that abnormal signaling through CD4 may contribute to impaired tolerance and expansion of autoreactive T cells exhibited in MRL-lpr/lpr mice.