Extensive chronic graft-versus-host disease (ecGVHD) is characterized by fibrosis similar to that of patients with systemic sclerosis (scleroderma). Since stimulatory autoantibodies against the platelet-derived growth factor (PDGF) receptor (PDGFR) have been found in patients with scleroderma and are responsible for the activation of skin fibroblasts, we tested the hypothesis that these autoantibodies are also present in patients affected by ecGVHD. Serum from 39 patients subjected to allogeneic stem cell transplantation for hematologic malignan-

IntroductionAbnormal oxidative stress has been described in systemic sclerosis (SSc) and previous works from our laboratory demonstrated an increased generation of reactive oxygen species (ROS) by SSc fibroblasts and monocytes. This study investigated the ability of SSc T lymphocytes to produce ROS, the molecular pathway involved, and the biological effects of ROS on SSc phenotype.MethodsPeripheral blood T lymphocytes were isolated from serum of healthy controls or SSc patients by negative selection with magnetic beads and activated either with PMA or with magnetic beads coated with anti-CD3 and anti-CD28 antibodies. Intracellular ROS generation was measured using a DCFH-DA assay in a plate reader fluorimeter or by FACS analysis. CD69 expression and cytokine production were analyzed by FACS analysis. Protein expression was studied using immunoblotting techniques and mRNA levels were quantified by real-time PCR. Cell proliferation was carried out using a BrdU incorporation assay.ResultsPeripheral blood T lymphocytes from SSc patients showed an increased ROS production compared to T cells from healthy subjects. Since NADPH oxidase complex is involved in oxidative stress in SSc and we found high levels of gp91phox in SSc T cells, SSc T cells were incubated with chemical inhibititors or specific siRNAs against gp91phox. Inhibition of NADPH oxidase partially reverted CD69 activation and proliferation rate increase, and significantly influenced cytokine production and ERK1/2 activation.ConclusionsSSc T lymphocityes are characterized by high levels of ROS, generated by NADPH oxidase via ERK1/2 phosphorylation, that are essential for cell activation, proliferation, and cytokine production. These data confirm lymphocytes as key cellular players in the pathogenesis of systemic sclerosis and suggest a crucial link between ROS and T cell activation.Electronic supplementary materialThe online version of this article (doi:10.1186/s13075-015-0591-8) contains supplementary material, which is available to authorized users.

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Background Experimental data are consistent with the hypothesis that activation of the PDGF receptor (PDGFR) is characteristic of scleroderma (SSc) fibroblasts and may contribute to their activation. We have recently demonstrated that fibroblasts from SSc patients contain high Ha Ras and ROS (Reactive Oxygen Species) levels and constitutive activation of ERK1/2 (Svegliati et al: JBC in press). Furthermore, SSc patients have circulating auto-antibodies against the PDGFR which induce type I collagen gene expression in normal human fibroblasts through the Ha Ras-ERK1/2- ROS pathway (Svegliati et al: Submitted). These findings suggest that anti PDGFR auto-antibodies play a pivotal role in the pathogenesis of scleroderma. Clinical chronic graft-versus-host disease (cGVHD) can show manifestations that are very similar to those of SSc. Although it is conceivable that the two diseases can share a similar pathophysiological mechanism there are no data supporting this assumption. In view of these considerations we tested the hypothesis that patients with cGVHD have serum auto-antibodies that stimulate PDGFR and activate collagen gene expression in fibroblasts. Methods Serum from 7 patients with extensive cGVHD showing scleroderma-like features either in the skin or in the lung was analyzed for the presence of stimulatory autoantibodies to PDGFR. Patients receiving allogeneic transplantation, but without any signs of cGVHD were used as controls. The median F-U after transplant was 23 months (range 16–36) in patients with cGVH and 42 (range 9–51) in the control group. The assay was carried by incubating purified IgG of the patients with mouse embryo fibroblasts carrying inactive copies of PDGFR α or β chains (PDGFR −/−) or the same cells expressing PDGFR α or β, respectively. Production of reactive oxygen species was assayed in the presence or absence of specific PDGFR inhibitors. The antibodies were characterized by immunoprecipitation, immunoblotting and absorption experiments in primary human fibroblasts and endothelial cells. Result Stimulatory antibodies to the PDGFR were selectively found in all patients with cGVHD and fibrotic lesions. The antibodies specifically recognized PDGFR, induced tyrosine phosphorylation and ROS accumulation. Their activity was completely and selectively abolished by pre-incubation with cells expressing PDGFR α or β chains or by PDGF receptor tyrosine kinase inhibitor. Anti-PDGFR antibodies induced selectively Ha-Ras-ERK1/2 and ROS cascade and stimulated the expression of type I collagen gene and myofibroblast phenotype conversion in normal human primary fibroblasts. Antibodies were absent in all controls. Conclusions Stimulatory auto-antibodies against PDGFR represent a specific hallmark of patients with cGVHD. Their biological activity on fibroblasts strongly argues for a causal role in the pathogenesis of the disease.