Absolute reduction of peripheral regulatory T cell in patients with relapsing polychondritis.

Objectives: Although relapsing polychondritis (RP) is considered as an immune-mediated systemic disease, the levels of peripheral lymphocyte subpopulations are rarely studied in patients with RP. In this study, we focused on changes of peripheral CD4+T cell subsets in patients with RP.

Methods: Absolute numbers and percentages of CD4+T cell subsets including helper T(Th)1, Th2, Th17 cells and regulatory T (Treg) cells in peripheral blood (PB) from 19 RP patients, healthy controls and RA patients respectively were assessed by flow cytometry combined a microbead-based single-platform method. We compared the CD4+T cell levels in all RP patients and healthy controls. In addition, we analysed the difference of the absolute number and percentage of Treg cells between RP and RA patients.

Results: Compared with healthy controls, all RP patients had significantly both lower absolute number and proportion of Treg cells (absolute number, 45.10/μl vs. 22.48/μl, p<0.001; proportion, 5.19% vs. 3.78%, p<0.001) no matter whether they had received treatment or not. Similarly, the absolute number of Th2 cells in all RP patients was decreased (10.19/μl vs. 7.44/μl, p=0.030). However, there were no significant differences in percentages and absolute numbers of Th1 and Th17 cells between RP patients and healthy controls. The above results led to increased ratios of Th1/Treg (3.68 vs. 2.06, p=0.020), Th2/Treg (0.29 vs. 0.21, p=0.037) and Th17/Treg (0.25 vs. 0.14, p<0.001) in RP patients, and untreated RP patients were mainly characterised by the imbalance of Th17/Treg (0.25 vs. 0.14, p<0.01). There was no significant difference in Treg cells between RP and RA patients (p>0.05).

Conclusions: Our data suggest that the reduction of Treg cells and its imbalance with Th cells play an important role in the pathogenesis of RP.