Normal Treg function at the site of inflammation, but resistance of effector cells to suppression of cell proliferation. PBMCs and SFMCs were isolated from paired PB and SF samples from JIA patients. CD4⁺CD25⁺CD127^low Tregs were sorted from PBMCs by flow cytometry and cocultured with CFSE-labeled PBMCs (black bars) or SFMCs (dark gray bars) at 1:8 and 1:4 ratios. Conversely, CD4⁺CD25⁺CD127^low Tregs were sorted from SFMCs and cocultured with CFSE- labeled PBMCs (light gray bars) or SFMCs (white bars). At day 4, suppression of CD4⁺ (A) and CD8⁺ T-cell proliferation (B) was measured. The results show percentage of suppression in the presence of Tregs relative to effector cells alone. Bars represent mean ± SEM of n = 2, *P < .05 compared with PB-Tr + PBMCs.