The Division of Rheumatology and Immunology is known for its basic and clinical research on systemic lupus erythematosus (SLE). SLE is a disorder of generalized autoimmunity induced by self-reactive T cells when immune regulation fails. We have taken advantage of the exceptional clinical resources of the LAC+USC Medical Center to study the genetic basis of SLE and to elucidate the cellular mechanisms responsible for immune dysregulation in this disease. Beginning with the efforts of the late Edmund Dubois, this Division is well known for its observations on the clinical and laboratory manifestations of systemic lupus erythematosus (SLE), the prototype of the human autoimmune diseases. Drs. Horwitz, Gray and Stohl have taken advantage of the extraordinary clinical resources of the Keck School of Medicine to study immune regulation in human SLE. These resources include the LAC+USC Medical Center, the largest public hospital in the United States, and the USC International Twin Registry where 160 lupus twins have been identified. Dr. Horwitz and his group have concentrated their efforts on T cells while Dr. William Stohl’s current work is focused on B cells. During the past year, information gained from the laboratory bench which either target T cells or B cells has served as the basis for novel treatment strategies.

Drs. Gray and Horwitz have been investigating the role of hormone-like growth factors called “cytokines” in immune regulation. They have shown that the cytokine, transforming growth factor beta (TGF-b) is a critical co-stimulatory factor in the generation of “immunologic policemen.” These policemen are T cells that suppress antibody production and cell-mediated immunity, (the functional properties of both T cells and B cells). These workers previously reported decreased lymphocyte production of TGF-b impaired in SLE and they believe that this defect strongly contributes to decreased regulatory T cell function in SLE. Recent studies suggest that regulatory T cell defects in SLE are reversible. Treatment of IL-2 activated SLE lymphocytes to TGF- b restored the ability of CD8+ T cells to decrease autoantibody production. Most recently, using a mouse model of lupus, they have successfully generated regulatory T cells ex-vivo and used these cells to suppress, if not prevent, the development of lupus in vivo. The next step is to restore the ability of T cells from patients with human SLE to suppress antibody production. To accomplish this objective, they plan to obtain large numbers of T cells from lupus patients by apheresis and use the methods described above to induce these cells to develop regulatory activity. After the cells are expanded, they will be infused back to the patient. The patients will then be carefully monitored for suppression of autoimmunity and clinical improvement. If successful, a particular advantage of this novel therapeutic approach is that it would avoid the severe toxic side effects associated with the drugs now used to treat patients with SLE and other chronic, inflammatory autoimmune diseases.

Previously, Dr. Stohl and his colleagues had demonstrated that levels of a potent B cell growth factor called “B Lymphocyte Stimulating Factor (BLyS)” are elevated in a substantial fraction of SLE patients. He and his colleagues are now investigating the role for BLyS overproduction in the development of SLE and are testing the ability of specific antagonists of BLyS to treat patients with SLE. In addition to generating T cells that down-regulate antibody production, Drs. Horwitz and Gray have successfully induced another subset of T cells to inhibit cell-mediated immunity. They have expanded a minor thymic-derived T cell subset to numbers that have powerful immunosuppressive properties. These cells may not only have the potential to prevent autoimmunity, but also may block the rejection of tissues transplanted from one individual to another. Allogeneic stem cell transplantation has significant potential in the treatment of individuals with hematologic and solid tumors, but this procedure has had limited usefulness because of graft-versus-host disease. The generation of regulatory T cells ex-vivo has the potential to prevent graftversus- host disease. In addition, kidney, heart and liver transplantation have increasing indications, but require toxic drugs to prevent rejection. The treatment of patients who receive these organ grafts with regulatory T cells has the potential result in long term survival without the use of these toxic drugs.

Novel approaches to treat patients with rheumatoid arthritis. Drs. Dan Arkfeld, Glenn Ehresmann and David Horwitz have been investigating new strategies to treat patients with rheumatoid arthritis (RA). This disease affects two million Americans, predominantly women, who suffer from the often crippling effects of this disease. Although the exact cause of RA is not established, most agree it is an autoimmune disease where cells called lymphocytes attack the body instead of eliminating foreign invaders. Lymphocytes called “CD4+ T cells” are involved in the initiation of RA. Macrophages and other cells in synovial joints then invade and destroy joint cartilage. Drs. Arkfeld, Ehresmann and Horwitz have been studying Therafectin (amiprilose hydrochloride) in the management of RA. The studies at USC have revealed that this drug is effective in patients with severe rheumatoid arthritis. The especially encouraging feature of Therafectin is that the drug appears to be much less toxic than most of the remittive drugs now in use for the treatment of RA.

Faculty Research Areas

Daniel G. Arkfeld, M.D.
Rheumatoid Arthritis
Osteoarthritis
Novel Immune Therapies for Immune Disorders

David A. Horwitz, M.D.
Cytokine-Mediated Down-Regulation of B Cell Hyperactivity in SLE
Immunoregulatory Mechanisms in the Rheumatic Diseases
Regulatory T Cell Subsets in SL

William Stohl, M.D., Ph.D.
T Cell Regulation of Polyclonal Immunoglobulin and Autoantibody Production in SLE and Related Rheumatological Diseases
T Cell Helper and Down regulatory Functions Triggered by Microbial Superantigens.

Song Guo Zheng, M.D.
Treatment of Autoimmune Diseases
Prevention of Transplant Organ Rejection

Special Basic Research Activities

William Stohl, M.D., Ph.D.
Systemic Lupus Erythematosus and B lymphocyte stimulator (BLyS). Published observations in murine SLE strongly intimate a pathogenic role for excessive production of BLyS, a recently discovered member of the tumor necrosis factor (TNF) ligand superfamily that stimulates B cells in a T cell-independent manner. Published observations from our laboratory indicate that serum BLyS levels are elevated in many human SLE patients. Candidate BLyS antagonists have been developed and are being actively tested in clinical trials. Studies in mouse models of SLE are ongoing to elucidate the mechanisms through which overexpression of BLyS leads to clinical disease.

David A. Horwitz, M.D.
Cytokine-Mediated Down-Regulation of B Cell Hyperactivity in SLE. SLE is a disease of generalized autoimmunity characterized by B cell hyperactivity and the production of many autoantibodies. Our working hypothesis is that SLE patients are deficient producers of the cytokines required for the induction of the regulatory T cells which prevent autoimmunity. The principal goals of this project are to restore the capacity of SLE T cells to down-regulate antibody production, define the cytokine networks involved, and use this information to prepare for clinical trials where we will learn whether normalization of T regulatory cell activity can lead to disease remission. We have learned that Transforming Growth Factor beta (TGF- b) is an important costimulatory factor in the generation of CD8+ cells which down-regulate T cell-dependent antibody production, that production of lymphocyte-derived TGF- b is decreased in SLE, and that exposure of SLE PBMC to IL-2 and TGF-b markedly decreased spontaneous polyclonal and autoantibody production. The specific aims of the present proposal are: 1) To determine whether CD4+ T cells activated in the presence of TGF-b also develop the capacity to down-regulate IgG production. If so, we will determine whether they retain their regulatory effects after expansion; 2) To test the hypothesis that IL-10 can be down-regulated by TGF- b, and that decreased amounts of lymphocyte-derived TGF- b in SLE contributes to elevated levels of IL-10; 3) To learn whether T regulatory cells generated ex-vivo and adoptively transferred to NZM2410 mice can delay the onset of SLE. Ultimately, we plan to condition T cells of SLE patients with cytokines ex-vivo to develop down-regulatory activity and learn whether the adoptive transfer of these cells back to the patient will have beneficial therapeutic effects. We intend to establish proof of the concept that regulatory T cells generated ex-vivo using TGF- b and adoptively transferred to patients with SLE can correct a pathogenic immune defect and have beneficial clinical effects on the course of this autoimmune disorder. We have planned to test this hypothesis using two animal models of SLE. In preparation for a Phase 1 clinical study in human SLE, we also plan to determine the optimal composition of regulatory T cells for adoptive transfer, elucidate reversible defects of regulatory cell differentiation in SLE, and learn whether these regulatory T cells can be expanded. Our immediate objective during this project period is to learn how TGF- b induces immature CD4+ and CD8+ lymphocytes to develop suppressive activity. The project has three parts. This information will be very helpful in the design of studies to assess the suppressive effects of these regulatory T cells in vivo.

Special Clinical Research Activities

William Stohl, M.D., Ph.D.
Phase 2 Studies of Lymphostat-BTM (Monoclonal Anti-BLyS Antibody) in Subjects with Systemic Lupus Erythematosus (SLE) and Rheumatoid Arthritis (RA). The current paradigm of SLE and RA pathogenesis begins with a genetic predisposition leading to the production of pathogenic autoantibodies and autoreactive effector B and T lymphocytes. The rational for developing a BLyS antagonist for treatment of autoimmune disease is supported in the current literature. For example, constitutive overexpression of BLyS in transgenic mice results in the development of autoimmune-like disease characterized by hypergammaglobulinemia, autoantibody production (e.g., anti-dsDNA antibodies, rheumatoid factor antibodies), and kidney involvement. Soluble BLyS receptor (TACI-Fc), as a BLyS antagonist, inhibits proteinuria in, and prolongs the survival of, NZBWF1 mice. TACI-Fc also reduces disease severity in an animal model of RA. Elevated BLyS levels are evident in the serum and synovial fluid of some RA patients and the serum of SLE patients. A positive correlation exists between serum BLyS and serum IgG levels and autoantibody (anti-dsDNA and RF) levels. Taken together, these data provide evidence that BLyS antagonism has potential therapeutic benefit in SLE and RA.