The induction of organ-specific antibodies during the graft-vs.-host reaction

Rapamycin Treatment Alleviates Chronic GVHD-Induced Lupus Nephritis in Mice by Recovering IL-2 Production and Regulatory T Cells While Inhibiting Effector T Cells Activation

In this study, we test the therapeutic effects of rapamycin in a murine model of SLE-like experimental lupus nephritis induced by chronic graft-versus-host disease (cGVHD). Our results suggest that rapamycin treatment reduced autoantibody production, inhibited T lymphocyte and subsequent B cell activation, and reduced inflammatory cytokine and chemokine production, thereby protecting renal function and alleviating histological lupus nephritis by reducing the occurrence of albuminuria. To explore the potential mechanism of rapamycin's reduction of kidney damage in mice with lupus nephritis, a series of functional assays were conducted. As expected, rapamycin remarkably inhibited the lymphocytes' proliferation within the morbid mice. Interestingly, significantly increased proportions of peripheral CD4+FOXP3+ and CD4+CD25high T cells were observed in rapamycin-treated group animals, suggesting an up-regulation of regulatory T cells (Tregs) in the periphery by rapamycin treatment. Furthermore, consistent with the results regarding changes in mRNA abundance in kidney by real-time PCR analysis, intracellular cytokine staining demonstrated that rapamycin treatment remarkably diminished the secretion of Th1 and Th2 cytokines, including IFN-γ, IL-4 and IL-10, in splenocytes of the morbid mice. However, the production of IL-2 from splenocytes in rapamycin-treated mice was significantly higher than in the cells from control group animals. These findings suggest that rapamycin treatment might alleviate systemic lupus erythematosus (SLE)-like experimental lupus nephritis through the recovery of IL-2 production, which promotes the expansion of regulatory T cells while inhibiting effector T cell activation. Our studies demonstrated that, unlike other commonly used immunosuppressants, rapamycin does not appear to interfere with tolerance induction but permits the expansion and suppressive function of Tregs in vivo.

Isogarcinol Extracted from Garcinia mangostana L. Ameliorates Systemic Lupus Erythematosus-like Disease in a Murine Model

Isogarcinol is a new immunosuppressant that we extracted from Garcinia mangostana L. In the present study, we elucidate its beneficial effect in chronic graft-versus-host disease (cGVHD) in mice -- a model for systemic lupus erythematosus (SLE) in human. The oral administration of 60 mg/kg isogarcinol significantly reduced proteinuria, corrected the abnormal serum biochemical indicator, and decreased the amount of serum antibodies and lowered the renal histopathology score. In addition, isogarcinol alleviated the abnormal activation of CD4 T cells and decreased the expression of inflammatory genes and cytokines in the kidneys and peritoneal macrophages. The mechanism of action of isogarcinol is associated with downregulation of CD4 T cells and inflammatory effects. Therefore, we believe that isogarcinol may be a potential therapeutic drug candidate for future treatment of SLE.

CD3 mAb treatment ameliorated the severity of the cGVHD-induced lupus nephritis in mice by up-regulation of Foxp3+ regulatory T cells in the target tissue: kidney

Teff/Treg imbalance orchestrated the onset and the progression of the lupus nephritis in a DBA/2→B6D2F1 murine model with cGVHD. In this paper, we first used 145-2C11 Ab to treat these human SLE-like diseased animals. The results showed that short-term low-dose anti-CD3 antibody treatment induced a significant remission of established proteinuria, production of autoantibodies, immune complex deposition and renal parenchyma lesions in lupus nephritic mice. Of note, we found a robust up-regulation of Foxp3 mRNA expression in the target tissue: kidney from mice with anti-CD3 antibody treatment compared to those with control IgG treatment. Likewise, an increased renal mRNA abundance for IL-10 was also observed in anti-CD3 antibody treated mice. In contrast, genes associated with inflammation and fibrosis as well as cytokines related to effector T cell responses were down-regulated by anti-CD3 mAb treatment. These findings suggested that short-term low-dose anti-CD3 antibody treatment might induced an IL-10-secreting Foxp3(+) regulatory T cells in this cGVHD target tissue: kidney, that suppressed the activation of effector T cells (Th1, Th2 and Th17), thus ameliorating the severity of the lupus nephritis in mice.

Mouse models of bone marrow transplantation

Over the last 50 years, mouse models of bone marrow transplantation have provided the critical links between graft-versus-host disease (GVHD) and graft-versus-leukemia (GVL) pathophysiology and clinical practice. The initial insight from mouse models that GVHD and GVL were T cell dependent has long been confirmed clinically. More recent translations from mouse models have included the important role of inflammatory cytokines in GVHD. Newly developed concepts relating to the ability of antigen presenting cell (APC) and T cell subsets to mediate GVHD now promise significant clinical advances. The ability to use knockout and transgenic approaches to dissect mechanisms of GVHD and GVL mean that mouse systems will continue as the predominant preclinical platform. The basic transplant approach in these models, coupled with modern "real-time" immunologic imaging of GVHD and GVL is discussed.

Animal models of acute and chronic graft-versus-host disease

Graft-versus-host disease (GVHD) represents a special situation in transplantation immunology in which immunocompetent donor cells are engrafted into recipients that are incapable of rejecting them due to tolerance, immaturity, or radiation- or chemotherapy-induced immune deficiency. Donor T cells encountering allogeneic stimulators become activated, secrete cytokines, proliferate, and differentiate into effectors; this in vivo immune response is known as the graft-versus-host reaction (GVHR). The systemic effects of this initial donor anti-host reaction comprise a multiorgan syndrome, graft-versus-host disease (GVHD). Murine GVHD experiments have been utilized to model the clinical disorders of acute and chronic GVHD (AGVHD and CGVHD) that occur after allogeneic bone marrow transplantation, and also to study T cell regulation, induction of tolerance, and autoimmune diseases. Presented in this unit are methods for generating and assessing both AGVHD and CGVHD in mice. While the two syndromes differ markedly in immunopathogenesis, both can be induced by the two main methods presented: transfer of allogenic donor lymphocytes and stem cells into irradiated hosts, and transfer of parental strain lymphocytes and stem cells into unirradiated, immune-competent F1 strain hosts. Several endpoints of AGVHD and CGVHD should be evaluated in experimental mice, with comparisons made to the syngeneic transplant control or the T cell-depleted allogeneic control. To this end, protocols are provided for the assessment of survival rates, weight loss, chimerism, donor-host cytotoxicity, and cytokine and proliferative responses to mitogenic or allogeneic stimuli. Histopathology and assays of B cell immune function are also described for evaluation of the pathogenesis of GVHD.

Increased Severity of Murine Lupus in Female Mice Is Due to Enhanced Expansion of Pathogenic T Cells

A strong female predominance is a well-recognized feature of human lupus. The mechanism by which sex influences disease expression and severity is not fully understood. To address this question, we used the parent-into-F(1) (p-->F(1)) model of chronic graft-vs-host disease (cGVHD) in which lupus-like humoral autoimmunity and renal disease are induced in normal F(1) mice. An advantage of this model is that the pathogenic T cells driving disease (donor strain) can be studied separately from nonspecifically activated T cells (host strain). We observed that lupus-like disease using female donor and host mice (f-->F cGVHD) is characterized by more severe long-term disease (glomerulonephritis) than with male donor and host (m-->M cGVHD). Interestingly, differences in disease parameters could be seen at 2 wk after parental cell transfer, as evidenced by a 2- to 3-fold greater engraftment of donor CD4(+) T cells in f-->F cGVHD mice, which persisted throughout disease course. Enhanced engraftment of donor CD4(+) T cells in f-->F cGVHD mice was not due to differences in splenic homing, alloreactive precursor frequency, initial proliferation rates, or apoptotic rates, but rather to sustained high proliferation rates during wk 2 of disease compared with m-->M cGVHD mice. Crossover studies (m-->F, f-->M) demonstrated that enhanced donor CD4(+) T cell proliferation and engraftment segregate with the sex of the host. These results demonstrate that the sex of the recipient can influence the expansion of pathogenic T cells, thus increasing long-term the burden of autoreactive T cells and resulting in greater disease severity.

Progression from acute to chronic disease in a murine parent-into-F1 model of graft-versus-host disease

The parent-into-immunocompetent-F(1) model of graft-vs-host disease (GVHD) induces immune dysregulation, resulting in acute or chronic GVHD. The disease outcome is thought to be determined by the number of parental anti-F(1) CTL precursor cells present in the inoculum. Injection of C57BL/6 (B6) splenocytes into (B6 x DBA/2)F(1) (B6D2F(1)) mice (acute model) leads to extensive parental cell engraftment and early death, whereas injection of DBA/2 cells (chronic model) results in little parental cell engraftment and a lupus-like disease. This study demonstrated that injection of BALB/c splenocytes into (BALB/c x B6)F(1) (CB6F(1)) mice resulted in little engraftment of parental lymphocytes and the development of lupus as expected. Injection of B6 splenocytes into CB6F(1) initiated an initial burst of parental cell engraftment similar to that of B6 into B6D2F(1). However, the acute disease resolved, and the CB6F(1) mice went on to develop chronic GVHD with detectable Abs to ssDNA, dsDNA, and extractable nuclear Ags. Limiting dilution CTL assays determined that B6 splenocytes have CTL precursor frequencies of 1/1000 against both CB6F(1) and B6D2F(1), whereas DBA/2 and BALB/c splenocytes have a CTL precursor frequency of 1/20,000 for their respective F(1)s. The Th cell precursor frequency for B6 anti-DBA/2 was 3-fold higher than that for B6 anti-BALB/c determined by limiting dilution proliferation assays. These results indicate the importance of adequate allospecific helper as well as effector T cells for the induction and maintenance of acute GVHD in this model, and presents an unexpected model in which initial acute GVHD is replaced by the chronic form of disease.

The IgG2a antibody response to thyroglobulin is linked to the Igh locus in mouse

The IgG-subclass usage by several strains of mice in the response to immunization with mouse thyroglobulin (mTg) was examined in the experimental autoimmune thyroiditis model. While the subclass usage by most mouse strains was similar, the Ighb allotype-bearing mice consistently produced lower IgG2a levels to mTg. Using CBA-Ighb congenic and recombinant inbred strains of mice, the lower level of IgG2a in the Ighb mouse was mapped to the Igh locus. The regulation of IgG2a appeared to be cis controlled, as the CBA x C57BL/6F1 mouse also produced reduced IgG2a of the Ighb (B6) allotype but not of the Ighj (CBA) allotype.

Leflunomide (HWA 486), a novel immunomodulating compound for the treatment of autoimmune disorders and reactions leading to transplantation rejection

Leflunomide has been shown to be very effective in preventing and curing several autoimmune animal diseases. Further, this agent is as effective as cyclosporin A in preventing the rejection of skin and kidney transplants in rats. Preliminary results from patients suffering from severe cases of rheumatoid arthritis demonstrated that clinical and immunological parameters could be improved with leflunomide therapy. Mode of action studies revealed that this substance antagonizes the proliferation inducing activity of several cytokines and is cytostatic for certain cell types. In this light, we could show that tyrosine phosphorylation of the RR-SRC peptide substrate and the autophosphorylation of the epidermal growth factor (EGF) receptor were, dose dependently, inhibited by leflunomide. EGF activates the intrinsic tyrosine kinase of its receptor, which stimulates the phosphorylation of a variety of peptides, the amino acid residue in all cases is tyrosine. These results indicate that much of leflunomide's activity could be due to the inhibition of tyrosine-kinase(s), which is an important general mechanism for the proliferation of various cell types. Thus, leflunomide, which is effective against autoimmune diseases and reactions leading to graft rejection, would seem to have a mode of action separating it from known immunosuppressive drugs.

The frequency of LPS-responsive B cells to autologous and heterologous thyroglobulin

The frequency of precursors within the mouse splenic B cell pool, reactive with mouse thyroglobulin (mTg) was estimated using a limiting dilution assay system. The mean frequency was found to be 1/3900 B cells. The results provide a minimal estimate of the frequency of mTg-reactive B cells. The frequency of mTg-reactive B cells was not influenced by the MHC locus, as both high- and low-responder strains showed similar frequencies. While the frequency of B cells reactive to human Tg was found to be similar to that reactive to mTg, only 20% of the mTg-reactive clones also cross-react with human Tg. Similarly, only 30% of huTg reactive clones were found to react with mTg. Therefore, a large proportion of Tg-reactive antibodies are restricted to self-determinants and not determinants to conserved regions of the Tg molecule.

Persistence of allospecific helper T cells is required for maintaining autoantibody formation in lupus-like graft-versus-host disease

Induction of a graft-versus-host (GVH) reaction (GVHR) in non-irradiated (C57BL/10ScSn x DBA/2)F1 mice (BDF1) with DBA/2 lymphoid cells leads to chronic GVH disease (GVHD). One of the pathological alterations of this type of GVHD is hyperplasia of host B cells with production of lupus-like autoantibodies. This hyperstimulation of host B cells has previously been demonstrated to be induced by alloreactive donor T helper cells that were also proposed to maintain it. We provide three pieces of experimental evidence in support of this concept. First, treatment of mice with chronic GVHD by injection of monoclonal anti-Thy-1.2 antibodies, performed at week 6 after the injection of C57BL/6 lymphoid cells into (C57BL/6 x C57BL.bm12)F1 mice led to a significant decrease in the titre of anti-nuclear antibodies. Second, CD4+ donor T cells persisted in BDF1 mice with GVHD (GVHF1) for at least 10 weeks after the induction of GVHR; these T cells showed alloreactive helper activity against H-2b MHC determinants of the opposite parent in vitro. Third, T cells of GVHF1 mice, obtained 2 months after the induction of GVHR and transferred into normal secondary recipients, induced signs of chronic GVHD in DBF1 but not in DBA/2 mice. The combined results show that persisting donor T helper cells in GVHF1 mice retain their alloreactivity towards H-2 class II antigens for a long time after the induction of GVHR and they strongly suggest that these T cells are also the driving force behind the production of lupus-like autoantibodies at the late stage of chronic GVHD.

Pathogenic mechanisms in autoimmune diseases

Autoimmunity may be initiated by a variety of mechanisms involving changes in autologous antigens or alterations in immune regulation. Autoimmune disease, the pathological consequence of an autoimmune response, depends principally upon the stimulation of helper/inducer T cells reactive with self-antigens. Such T cells direct the quantity and quality of the immune response by influencing the mixture of interleukins produced. Autoantibodies react with accessible cells and mediate injury directly or indirectly. Delayed hypersensitivity reactions indirectly damage tissues through the agency of lymphokines. Cytotoxic T cells penetrate tissue spaces and attack cells bearing requisite surface antigens complexed with the appropriate major histocompatibility complex product. Macrophages and NK cells, activated by lymphokines, have potential to augment tissue damage. These several mechanisms do not operate in isolation; rather, multiple processes act in unison in most autoimmune diseases.

Mercuric chloride induces autoantibodies against U3 small nuclear ribonucleoprotein in susceptible mice

Autoantibodies to nucleolar components are a common serological feature of patients suffering from scleroderma, a collagen vascular autoimmune disease. While animal models, which spontaneously develop abundant anti-nucleolar antibodies, have not yet been described, high titers of such antibodies may be induced by treating susceptible strains of mice with mercuric chloride. We have identified the nucleolar autoantigen against which the HgCl2-induced IgG autoantibodies from mice of strain B10.S are directed. It is a protein with an apparent molecular mass of 36 kDa and a pI value of approximately 8.6, which is associated with the nucleolar small nuclear RNA U3, and by these criteria must be identical with a polypeptide called fibrillarin. It is striking that scleroderma patients spontaneously produce autoantibodies against the same U3 ribonucleoprotein (RNP). The HgCl2-induced murine and the scleroderma-specific human anti-U3 RNP autoantibodies were indistinguishable in their reactivities toward fibrillarin. They further resemble each other insofar as both recognize epitopes on the 36-kDa protein, which have been highly conserved throughout evolution. Our results provide a basis to investigate at the molecular level whether similar immunoregulatory dysfunctions may lead to the preferential anti-U3 RNP autoantibody production in the animal model and in scleroderma patients.