Increased Frequency and Compromised Function of T Regulatory Cells in Systemic Sclerosis (SSc) Is Related to a Diminished CD69 and TGFb Expression

Background: Regulatory T cells (Tregs) are essential in the control of tolerance. Evidence implicates Tregs in human autoimmune conditions. Here we investigated their role in systemic sclerosis (SSc). Methods/Principal Findings: Patients were subdivided as having limited cutaneous SSc (lcSSc, n = 20) or diffuse cutaneous SSc (dcSSc, n = 48). Further subdivision was made between early dcSSc (n = 24) and late dcSSc (n = 24) based upon the duration of disease. 26 controls were studied for comparison. CD3+ cells were isolated using FACS and subsequently studied for the expression of CD4, CD8, CD25, FoxP3, CD127, CD62L, GITR, CD69 using flow cytometry. T cell suppression assays were performed using sorted CD4CD25CD127 and CD4CD25CD127 and CD3 cells. Suppressive function was correlated with CD69 surface expression and TGFb secretion/expression. The frequency of CD4CD25 and CD25FoxP3CD127 T cells was highly increased in all SSc subgroups. Although the expression of CD25 and GITR was comparable between groups, expression of CD62L and CD69 was dramatically lower in SSc patients, which correlated with a diminished suppressive function. Co-incubation of Tregs from healthy donors with plasma from SSc patients fully abrogated suppressive activity. Activation of Tregs from healthy donors or SSc patients with PHA significantly up regulated CD69 expression that could be inhibited by SSc plasma. Conclusions/Significance: These results indicate that soluble factors in SSc plasma inhibit Treg function specifically that is associated with altered Treg CD69 and TGFb expression. These data suggest that a defective Treg function may underlie the immune dysfunction in systemic sclerosis. Citation: Radstake TRDJ, van Bon L, Broen J, Wenink M, Santegoets K, et al. (2009) Increased Frequency and Compromised Function of T Regulatory Cells in Systemic Sclerosis (SSc) Is Related to a Diminished CD69 and TGFb Expression. PLoS ONE 4(6): e5981. doi:10.1371/journal.pone.0005981 Editor: Derya Unutmaz, New York University School of Medicine, United States of America Received April 20, 2009; Accepted May 23, 2009; Published June 22, 2009 Copyright: 2009 Radstake et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The Post-doctoral program (T.R.) was funded by the Niels-Stensen Foundation from The Netherlands. The work presented here was partly funded by the VIDI laureate (T.R) from the Dutch Organization of Research (NWO). Support was also provided by grants to R.L. from the National Institutes of Health, (NIAMS U01AR055063) and an unrestricted grant from the American Society for Scleroderma Research. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: [email protected]