BAFF Antagonist Attenuates the Development of Skin Fibrosis in Tight-Skin Mice

Is there a role for B-cell depletion as therapy for scleroderma? A case report and review of the literature

OBJECTIVES

Rituximab (RTX) has been successfully used in the treatment of several rheumatic diseases with an acceptable safety profile. We present herein a patient with systemic sclerosis (SSc) who exhibited significant improvement of his lung function and skin fibrosis following RTX administration, and review the literature regarding the role of B-cells in SSc and the potential efficacy of RTX in its treatment.

METHODS

We performed an internet search using the keywords systemic sclerosis, scleroderma, rituximab, B-cells, fibrosis, interstitial lung disease (ILD), and therapy.

RESULTS

Our patient, a 40-year old man with severe SSc-associated ILD, received 4 courses of RTX. The patient's lung function improved; forced vital capacity and diffusing capacity of carbon monoxide reached values of 35% and 33%, respectively, compared with 30% and 14% of pretreatment values. Skin thickening assessed clinically and histologically improved as well. Several lines of evidence suggest that B-cells may have a pathogenic role in SSc. B-cells from tight skin mice--an animal model of SSc--exhibit chronic hyperactivity; likewise, B-cells from patients with SSc overexpress CD19 and are chronically activated. Furthermore, studies have revealed that B-cell genes were specifically transcribed in SSc skin and that B-cell infiltration was a prominent feature of SSc-associated ILD. The potential clinical efficacy of RTX in SSc has been explored in a limited number of patients with encouraging results. Preliminary data suggest that RTX may favorably affect skin as well as lung disease in SSc.

CONCLUSIONS

Several basic research data underscore the potential pathogenic role of B-cells in SSc and clinical evidence suggests that RTX might be a therapeutic option in SSc. Large-scale multicenter studies are needed to evaluate the potential clinical efficacy of RTX in SSc.

B cell depletion with rituximab in patients with diffuse cutaneous systemic sclerosis

OBJECTIVE

To determine the safety of rituximab, to provide preliminary data regarding the potential efficacy of rituximab, and to investigate the effects of rituximab on autoimmunity and fibrosis in patients with diffuse cutaneous systemic sclerosis (dcSSc).

METHODS

Fifteen patients with dcSSc, all of whom experienced their first non-Raynaud's disease-associated disease manifestation within 18 months of trial entry, were recruited to receive 2 intravenous doses of rituximab (1,000 mg), administered 2 weeks apart. Safety, clinical, and exploratory outcomes were evaluated at baseline and at 6 months. The primary outcome was the change in the modified Rodnan skin thickness score (MRSS) at 6 months compared with baseline.

RESULTS

Adverse events included frequent infusion reactions and rare infections (urinary tract infection and dental abscess occurred in 1 patient each). The mean change in the MRSS between baseline and 6 months was not significant. Results of pulmonary function tests and other measures of major organ involvement were stable. The modest B cell infiltrates that were present in most skin biopsy specimens at baseline were completely depleted at 6 months in most patients. Autoantibody titers showed only modest and variable changes after treatment.

CONCLUSION

In this pilot study, treatment with rituximab appeared to be safe and well tolerated among patients with dcSSc. Rituximab treatment resulted in both depletion of circulating B cells and depletion of dermal B cells but had little effect on the levels of SSc-associated autoantibodies. Rituximab treatment did not appear to result in a significant beneficial effect on skin disease. The potential efficacy of rituximab in other organs such as the lung could not be clearly evaluated in this small open-label trial.

B-cell-directed therapy for inflammatory skin diseases

The basic understanding of inflammatory dermatoses and autoimmune-mediated skin disorders has greatly advanced and broadened our understanding of underlying immune mechanisms that shape the complex network of chronic inflammation and autoimmunity. The new treatment options for psoriasis exemplify how new insights into (auto)immune responses, especially the role and function of various immune cells and proinflammatory cytokines, may lead to new therapeutic strategies. The concept of targeting B cells in autoimmune-mediated disorders is closely related to the discovery of autoantibodies and their cellular origin. However, the appreciation of B cells in autoimmunity has significantly changed and is not limited to their role as progenitors of autoantibody secreting plasma cells. Recent investigations of various inflammatory skin diseases, that is, autoimmune blistering disorders, collagen vascular diseases, and atopic dermatitis, actually support the concept that B cells might be as important as T cells in the etiopathogenesis of these disorders. The striking clinical improvement seen in patients with rheumatoid arthritis following B-cell depletion with the anti-CD20 mAb rituximab has tremendously catalyzed the interest in B-cell-targeted therapies in different autoimmune diseases. Future translational and clinical investigations are mandatory to precisely define the role and the contribution of impaired B-cell function in (auto)immune-mediated skin diseases.

T cells, B cells, and polarized immune response in the pathogenesis of fibrosis and systemic sclerosis

PURPOSE OF REVIEW

A better comprehension of the interactions between cells of the adaptive immune system with fibroblasts and endothelial cells is required to understand abnormal extracellular matrix deposition, development of pathologic fibrosis, and vasculopathy.

RECENT FINDINGS

Skin T cells with high IL-4 production potential and peripheral blood T cells preferentially expressing chemokine receptors associated with Th2 functions are found in individuals with active systemic sclerosis. Animal models indicate that Th2 cells and IL-13 can induce muscular hypertrophy in pulmonary arterial vasculature. In bleomycin-induced fibrosis, B cells produce fibrogenic cytokines upon interaction of an endogenous ligand (hyaluronan) with toll-like receptor-4. In the sclerodermatous graft versus host model, the lack of tumor necrosis factor-production by CD4+ T cells is permissive for fibrosis development. Dermal fibrosis and capillary loss typical of systemic sclerosis can be reversible after high-dose immunosuppression and hematopoietic stem cell transplantation.

SUMMARY

Although immunosuppressive strategies to treat patients with systemic sclerosis and allied conditions are largely disappointing, thus indicating a permissive rather than causative role of immunoinflammatory events characteristic of the disease, new findings stress that cells of the adaptive immune system play important roles in assisting fibrogenesis and vascular abnormalities. This may help in identifying efficacious strategies aimed at their control.

CD19 regulates skin and lung fibrosis via Toll-like receptor signaling in a model of bleomycin-induced scleroderma

Mice subcutaneously injected with bleomycin, in an experimental model of human systemic sclerosis, develop cutaneous and lung fibrosis with autoantibody production. CD19 is a general "rheostat" that defines signaling thresholds critical for humoral immune responses, autoimmunity, and cytokine production. To determine the role of CD19 in the bleomycin-induced systemic sclerosis model, we investigated the development of fibrosis and autoimmunity in CD19-deficient mice. Bleomycin-treated wild-type mice exhibited dermal and lung fibrosis, hyper-gamma-globulinemia, autoantibody production, and enhanced serum and skin expression of various cytokines, including fibrogenic interleukin-4, interleukin-6, and transforming growth factor-beta1, all of which were inhibited by CD19 deficiency. Bleomycin treatment enhanced hyaluronan production in the skin, lung, and sera. Addition of hyaluronan, an endogenous ligand for Toll-like receptor (TLR) 2 and TLR4, stimulated B cells to produce various cytokines, primarily through TLR4; CD19 deficiency suppressed this stimulation. These results suggest that bleomycin induces fibrosis by enhancing hyaluronan production, which activates B cells to produce fibrogenic cytokines mainly via TLR4 and induce autoantibody production, and that CD19 deficiency suppresses fibrosis and autoantibody production by inhibiting TLR4 signals.