Sustained improvement in rheumatoid arthritis following a protocol designed to deplete B lymphocytes

Rituximab: Ongoing and future clinical development

Monoclonal antibodies have been used as therapeutic agents for many years. In 1997, rituximab (Rituxan; Genentech, Inc, South San Francisco, CA, and IDEC Pharmaceuticals, San Diego, CA) became the first monoclonal antibody to be approved by the US Food and Drug Administration for a cancer indication. The use of rituximab in the treatment of low-grade or follicular, relapsed, or refractory CD20-positive B-cell non-Hodgkin's lymphoma was approved in November 1997 for United States marketing under the trade name Rituxan. In June 1998, rituximab was approved for all European Union countries under the trade name MabThera as therapy for patients with stage III/IV, follicular, chemoresistant, or relapsed (≥ 2 relapses) non-Hodgkin's lymphoma. To date, rituximab has been approved in 56 countries. Over 125,000 patients have been treated with this antibody in the United States alone. Rituximab served to heighten interest in the therapeutic applications of monoclonal antibodies. Literally dozens of antibodies are currently under investigation for a variety of malignant and non-neoplastic indications. The US Food and Drug Administration approved a new (revised) package insert in early 2001. These revisions have been communicated to physicians via a "Dear Doctor Letter" and will appear in the 2002 edition of the Physicians' Desk Reference. A significant amount of clinical research has been performed over the past 9 years, which has served to further our understanding of the potential clinical applications for this novel therapeutic agent. Ongoing and future clinical trials are reviewed in this article. However, much remains to be accomplished in key areas such as combinations with chemotherapy, biologics (including other antibodies), and radiotherapy/radioimmunotherapy; its role within multimodality regimens; and other malignant (beyond low-grade non-Hodgkin's lymphoma) and nonmalignant applications. Semin Oncol 29 (suppl 2):105-112. Copyright © 2002 by W.B. Saunders Company.

Rituximab: clinical development and future directions

The availability of effective monoclonal antibodies (mAbs) has revolutionised the management of patients with B-cell malignancies. The most widely studied of these agents is rituximab (Rituxan, IDEC Pharmaceuticals, San Diego, CA), a chimeric anti-CD20 antibody. Using the standard 4-weekly administration schedule, rituximab induces responses in almost half of patients with relapsed follicular/low-grade (F/LG) non-Hodgkin's lymphoma (NHL) with complete remissions in 6%. Lower response rates (RRs) have been noted in chronic lymphocytic leukaemia (CLL) using the standard dose and schedule. The drug has been well tolerated in most patients with common adverse events including mild to moderate fevers and chills and rare occurrences of a serious syndrome related to cytokine release and rapid tumour clearance. This antibody is also active against aggressive NHL, mantle cell NHL, post-transplant lymphoproliferative disorder (PTLD), lymphoplasmacytic NHL and hairy cell leukaemia and is also being evaluated in autoimmune disorders. Combinations of rituximab with chemotherapy regimens such as CHOP (cyclophosphamide, adriamycin, vincristine, predinisone) may alter the therapeutic paradigm for these diseases. The future promise of this antibody is a foundation on which to develop new strategies to increase the cure of patients with lymphoid malignancies.

From T to B and back again: positive feedback in systemic autoimmune disease

Systemic lupus erythematosus, a prototypical systemic autoimmune disease, is the result of a series of interactions within the immune system that ultimately lead to the loss of self-tolerance to nuclear autoantigens. Here, we present an integrated model that explains how self-tolerance is initially lost and how the loss of tolerance is then amplified and maintained as a chronic autoimmune state. Key to this model are the self-reinforcing interactions of T and B cells, which we suggest lead to perpetuation of autoimmunity as well as its spread to multiple autoantigen targets.

T cell activation in rheumatoid synovium is B cell dependent

Rheumatoid arthritis results from a T cell-driven inflammation in the synovial membrane that is frequently associated with the formation of tertiary lymphoid structures. The significance of this extranodal lymphoid neogenesis is unknown. Microdissection was used to isolate CD4 T cells residing in synovial tissue T cell/B cell follicles. CD4 T cells with identical TCR sequences were represented in independent, nonadjacent follicles, suggesting recognition of the same Ag in different germinal centers. When adoptively transferred into rheumatoid arthritis synovium-SCID mouse chimeras, these CD4 T cell clones enhanced the production of IFN-gamma, IL-1beta, and TNF-alpha. In vivo activity of adoptively transferred CD4 T cells required matching of HLA-DRB1 alleles and also the presence of T cell/B cell follicles. HLA-DRB1-matched synovial tissues that were infiltrated by T cells, macrophages, and dendritic cells, but that lacked B cells, did not support the activation of adoptively transferred CD4 T cell clones, raising the possibility that B cells provided a critical function in T cell activation or harbored the relevant Ag. Dependence of T cell activation on B cells was confirmed in B cell depletion studies. Treatment of chimeric mice with anti-CD20 mAb inhibited the production of IFN-gamma and IL-1beta, indicating that APCs other than B cells could not substitute in maintaining T cell activation. The central role of B cells in synovial inflammation identifies them as excellent targets for immunosuppressive therapy.

Chronic graft-versus-host disease: clinical manifestation and therapy

Chronic graft-versus-host disease (GVHD) is a major cause of morbidity and mortality in long-term survivors of allogeneic stem cell transplantation. The immunopathogenesis of chronic GVHD is, in part, TH-2 mediated, resulting in a syndrome of immunodeficiency and an autoimmune disorder. The most important risk factor for chronic GVHD is prior history of acute GVHD and strategies that prevent acute GVHD also decrease the risk of chronic GVHD. Other important risk factors are the use of a non-T cell-depleted graft, and older age of donor and recipient. Whether recipients of peripheral blood stem cells are at increased risk of chronic GVHD remains unsettled. There are no known pharmacologic agents which can specifically prevent development of chronic GVHD. Agents which have efficacy in the treatment of autoimmune disorders have been utilized as therapy for established chronic GVHD and are associated with response rates of 20% to 80%. Most responses are confined to skin, soft tissue, oral mucosa and occasionally liver. Bronchiolitis obliterans responds infrequently to therapy and is associated with a dismal prognosis. Newer, promising therapeutic strategies under investigation include thalidomide, photopheresis therapy, anti-tumor necrosis factor and B cell depletion with anti-CD20 monoclonal antibody.

Recent progress in the understanding of B-cell functions in autoimmunity

Our early concepts of the normal role of B cells in immunity focused on their ability to produce antibodies (Ab) and in the case of autoimmune diseases autoAbs, some of which were pathogenic. Over the past 10 years, it has became apparent that B cells display a variety of characteristics, other than Ab production, which could contribute to autoimmunity. They normally play a role in the development of lymphoid architecture, regulating T-cell subsets and dendritic cell (DC) function through cytokine production, and in activation of T cells. Receptors editing is also important in B cells which aids in immunity to infection and, possibly, prevention of autoimmunity. Transgenic animal models have now shown that B cells are necessary for many autoimmune diseases although their Ab products are not required in some cases. Negative signalling by CD5 and other molecules, such as CD22, in maintaining tolerance through recruitment of src-homology two domain-containing protein tyrosine phosphatase-1 has also been documented. In fact, we have now reached a new era whereby the B cell has returned as an important contributor to autoimmune disorders, so that the race is on to characterize signalling regulation via the B-cell receptor and coreceptors. Identification of such molecules and their potential defects should lead to effective ways of controlling the immune response and in particular preventing the development of autoimmune states. The classical view of B cells in the biology of immune responses to infectious and self-antigens (Ag) that they promote immunity primarily by producing Ab turns out to be rather naïve. Indeed, studies over the last few years indicate that this view is far from complete, and suggest that B lymphocytes have extraordinarily diverse functions within the immune system. Furthermore, it is becoming increasingly clear that the pathogenesis of autoimmune diseases cannot solely be accounted for by T cells, and intrinsic abnormalities of B cells have been described in such conditions. In this brief review we highlight some recent observations in the context of B lymphocyte in pathophysiology, and focus on their revival as pivotal players the pathophysiology in autoimmune diseases. Yet, it remains difficult to provide a model of how important B cells are in immunity and autoimmunity.