T cell subsets in experimental lupus nephritis: modulation by bacterial superantigen.
Chronic graft-vs-host disease (GvH), induced by injection of DBA/2 lymphocytes into (C57BL/6 x DBA/2)F1 hybrids, is a murine model for lupus nephritis, associated with a Th2-dependent polyclonal B cell activation. The development of glomerulosclerosis in this model is preceded by a glomerular influx of LFA-1+ T cells. We investigated whether exposure to bacterial superantigen would modulate the course of this autoimmune syndrome. Injection of the bacterial superantigen staphylococcal enterotoxin B (SEB) in mice has been shown to induce the activation of TcRVbeta8+ T cells. Within 2 weeks after GvH induction, mice were injected twice with 20 microg of SEB and the following parameters were examined: cytokine and Ig profile, proteinuria and renal pathology. The second SEB injection induced in GvH mice an increased release of both interferon-gamma (IFN-gamma) and interleukin-10 (IL-10) as compared with control F1 mice. No differences were observed in IL-2 production. SEB-treated GvH mice demonstrated a delayed onset of proteinuria. Histological analysis of the kidney showed that SEB-challenged GvH mice displayed significantly more interstitial inflammation and mesangial proliferation together with more IgG2a deposits in glomeruli than non-injected GvH mice. From these results, we conclude that GvH mice are more responsive to SEB in terms of cytokine production and that bacterial infection can modulate the course of this renal disease from a membranous to a more proliferative type of nephropathy. (+info)
Immunophilins, Refsum disease, and lupus nephritis: the peroxisomal enzyme phytanoyl-COA alpha-hydroxylase is a new FKBP-associated protein.
FKBP52 (FKBP59, FKBP4) is a "macro" immunophilin that, although sharing high structural and functional homologies in its amino-terminal domain with FKBP12 (FKBP1), does not have immunosuppressant activity when complexed with FK506, unlike FKBP12. To investigate the physiological function of FKBP52, we used the yeast two-hybrid system as an approach to find its potential protein partners and, from that, its cellular role. This methodology, which already has allowed us to find the FK506-binding protein (FKBP)-associated protein FAP48, also led to the detection of another FKBP-associated protein. Determination of the sequence of this protein permitted its identification as phytanoyl-CoA alpha-hydroxylase (PAHX), a peroxisomal enzyme that so far was unknown as an FKBP-associated protein. Inactivation of this enzyme is responsible for Refsum disease in humans. The protein also corresponds to the mouse protein LN1, which could be involved in the progress of lupus nephritis. We show here that PAHX has the physical capacity to interact with the FKBP12-like domain of FKBP52, but not with FKBP12, suggesting that it is a particular and specific target of FKBP52. Whereas the binding of calcineurin to FKBP12 is potentiated by FK506, the specific association of PAHX and FKBP52 is maintained in the presence of FK506. This observation suggests that PAHX is a serious candidate for studying the cellular signaling pathway(s) involving FKBP52 in the presence of immunosuppressant drugs. (+info)
Analysis of MHC class II genes in the susceptibility to lupus in New Zealand mice.
Hybrids of New Zealand Black (NZB) and New Zealand White (NZW) mice spontaneously develop a disease similar to human systemic lupus erythematosus. MHC and non-MHC genes contribute to disease susceptibility in this murine model. Multiple studies have shown that the NZW H2z locus is strongly associated with the development of lupus-like disease in these mice. The susceptibility gene(s) within H2z is not known, but different lines of evidence have pointed to class II MHC genes, either H2-E or H2-A (Ez or Az in NZW). Recent studies from our laboratory showed that Ez does not supplant H2z in the contribution to lupus-like disease. In the present work we generated C57BL/10 (B10) mice transgenic for Aaz and Abz genes (designated B10.Az mice) and used a (B10.Az x NZB)F1 x NZB backcross to assess the contributions of Az genes to disease. A subset of backcross mice produced high levels of IgG autoantibodies and developed severe nephritis. However, no autoimmune phenotype was linked to the Az transgenes. Surprisingly, in the same backcross mice, inheritance of H2b from the nonautoimmune B10 strain was strongly linked with both autoantibody production and nephritis. Taken together with our previous Ez studies, the present work calls into question the importance of class II MHC genes for lupus susceptibility in this model and provides new insight into the role of MHC in lupus-like autoimmunity. (+info)
Disparate T cell requirements of two subsets of lupus-specific autoantibodies in pristane-treated mice.
Intraperitoneal injection of pristane induces a lupus-like disease in BALB/c and other non-autoimmune mice characterized by autoantibody production and the development of immune complex disease closely resembling lupus nephritis. Two subsets of autoantibodies are induced by pristane: IgG anti-DNA DNA and -chromatin autoantibodies are strongly IL-6-dependent, whereas IgG anti-nRNP/Sm and -Su antibodies are not. The present studies were carried out to examine the role of T cells in establishing this dichotomy between the production of anti-nRNP/Sm/Su versus anti-DNA/chromatin autoantibodies. Autoantibody production and renal disease were evaluated in athymic (nude) mice treated with pristane. BALB/c nu/nu mice spontaneously developed IgM and IgG anti-single-stranded (ss)DNA and -chromatin, but not anti-nRNP/Sm or -Su, autoantibodies. Pristane treatment increased the levels of IgG anti-chromatin antibodies in nu/nu mice, but did not induce production of anti-nRNP/Sm or -Su antibodies. In contrast, BALB/c nu/+ and +/+ control mice did not spontaneously produce autoantibodies, whereas anti-nRNP/Sm and -Su autoantibodies were induced by pristane in approx. 50% of nu/+ and +/+ mice and anti-DNA/chromatin antibodies at lower frequencies. Nude mice spontaneously developed mild renal lesions that were marginally affected by pristane, but were generally milder than the lesions developing in pristane-treated nu/+ and +/+ mice. The data provide further evidence that two distinct pathways with different cytokine and T cell requirements are involved in autoantibody formation in pristane-induced lupus. This dichotomy may be relevant to understanding differences in the regulation of anti-DNA versus anti-nRNP/Sm autoantibodies in systemic lupus erythematosus, as well as the association of anti-DNA, but not anti-nRNP/Sm, with lupus nephritis. (+info)
Mycophenolate mofetil therapy in lupus nephritis: clinical observations.
Controlled clinical trials in renal transplantation have demonstrated that mycophenolate mofetil is well tolerated and has lower renal transplant rejection rates than azathioprine regimens. This study reports on the clinical experiences at two institutions with mycophenolate mofetil (MMF) for severe lupus nephritis. Twelve patients with relapsing or resistant nephritis previously treated with cyclophosphamide therapy and one patient who refused cyclophosphamide as initial therapy for diffuse proliferative nephritis but accepted MMF were included. During combined MMF/prednisone therapy, serum creatinine values remained normal or declined from elevated values: mean change in serum creatinine was -0.26+/-0.46 microM/L, P = 0.039. Proteinuria significantly decreased: mean change in urine protein-to-creatinine ratios was -2.53+/-3.76, P = 0.039. Decreased serum complement component C3 and elevated anti-double-stranded DNA antibody levels at baseline improved in some, but not all, patients. The mean initial dose of MMF was 0.92 g/d (range, 0.5 to 2 g/d). The mean duration of therapy was 12.9 mo (range, 3 to 24 mo). Adverse events included herpes simplex stomatitis associated with severe leukopenia (n = 1), asymptomatic leukopenia (n = 2), nausea/ diarrhea (n = 2), thinning of scalp hair (n = 1), pancreatitis (n = 1), and pneumonia without leukopenia (n = 1). Recurrence of the pancreatitis led to discontinuation of MMF in this patient; all other adverse events resolved with dose reduction. It is concluded that MMF is well tolerated and has possible efficacy in controlling major renal manifestations of systemic lupus erythematosus. Controlled clinical trials are needed to define the role of MMF in the management of lupus nephritis. (+info)
Mice with early onset of death (EOD) due to lupus glomerulonephritis.
Both MRL-lpr/lpr (lpr) and BXSB mice fall victim to autoimmune disease as a function of age. To combine their properties, brother-sister mating of (female lpr x male BXSB)F1 mice was done. Mice for mating were selected according to indicators of early onset of glomerulonephritis and subsequent early death (i.e., EOD). This mating was continued for more than 16 generations. The EOD mice thus established had homozygous H-2k/k, lpr/lpr, and possible yaa/- (in the case of males). The average life span of males was 83 days while that of females was 126 days. After 12 weeks of age, the majority (> 80%) of male EOD mice were characterized by the abnormality of urine due to glomerulonephritis. We then characterized how glomerulonephritis was evoked, especially in terms of expanding lymphocyte subsets in various immune organs. Similar to the case of parental lpr mice, the major expanding cells were CD4-8-B220+ TCRint cells in the immune organs and kidney. In addition, myeloid cells were found to infiltrate the kidney. This massive infiltration of both TCRint cells and myeloid cells might be responsible for the onset of acute glomerulonephritis. Even after more than 50 generations, these EOD mice still carry both lpr and yaa genes. These results suggest that EOD mice might be a very useful tool for the study of acute lupus glomerulonephritis which is evoked by the genetic abnormalities. (+info)
Antigen-specific therapy of murine lupus nephritis using nucleosomal peptides: tolerance spreading impairs pathogenic function of autoimmune T and B cells.
In the (SWR x NZB)F1 mouse model of lupus, we previously localized the critical autoepitopes for nephritogenic autoantibody-inducing Th cells in the core histones of nucleosomes at aa positions 10-33 of H2B and 16-39 and 71-94 of H4. A brief therapy with the peptides administered i.v. to 3-mo-old prenephritic (SWR x NZB)F1 mice that were already producing pathogenic autoantibodies markedly delayed the onset of severe lupus nephritis. Strikingly, chronic therapy with the peptides injected into 18-mo-old (SWR x NZB)F1 mice with established glomerulonephritis prolonged survival and even halted the progression of renal disease. Remarkably, tolerization with any one of the nucleosomal peptides impaired autoimmune T cell help, inhibiting the production of multiple pathogenic autoantibodies. However, cytokine production or proliferative responses to the peptides were not grossly changed by the therapy. Moreover, suppressor T cells were not detected in the treated mice. Most interestingly, the best therapeutic effect was obtained with nucleosomal peptide H416-39, which had a tolerogenic effect not only on autoimmune Th cells, but autoimmune B cells as well, because this peptide contained both T and B cell autoepitopes. These studies show that the pathogenic T and B cells of lupus, despite intrinsic defects in activation thresholds, are still susceptible to autoantigen-specific tolerogens. (+info)
Altered expression level of a systemic nuclear autoantigen determines the fate of immune response to self.
One of the hallmarks of systemic autoimmune diseases is immune responses to systemic nuclear autoantigens. We have examined the fate of the immune response against a nuclear autoantigen using human U1 small nuclear ribonucleoprotein-A protein (HuA) transgenic (Tg) mice by adoptive transfer of autoreactive lymphocytes. We obtained two Tg lines that have different expression levels of the transgene. After spleen cells from HuA-immunized wild-type mice were transferred to Tg mice and their non-Tg littermates, these recipients were injected with HuA/IFA to induce a recall memory response. HAB69, which expressed a lower amount of HuA, exhibited a vigorous increase in the autoantibody level and glomerulonephritis. Moreover, the autoreactivity spread to 70K autoantigen. Alternatively, in HAB64, which expressed a higher amount of HuA, the production of autoantibody was markedly suppressed. The immune response to HuA autoantigen was impaired as demonstrated in a both delayed-type hypersensitivity response and proliferation assay. This inhibition was Ag-specific and was mediated by T cells. These data suggest that the expression level of systemic autoantigens influences the outcome of the immune response to self. (+info)