GZMB and rheumatoid arthritis: GrB-producing Breg cells are significantly increased in patients with primary Sjögren’s syndrome and inflammatory bowel disease and are negatively correlated with disease activity.39 40 Our previous study also found functional impairments in GrB-producing Breg cells in patients with RA and SLE, which could be reversed after clinical remission.19 20 This study showed that GrB-producing Breg cells displayed potent regulatory properties and impaired GrB-producing Breg cells were present in lupus mice.