Rheumatoid arthritis (RA) is an autoimmune disorder in which immune cells attack the joints, causing inflammation, swelling, and erosion. Specific sets of immune cells, known as T cells, are responsible for inducing disease. In this issue of the Journal of Clinical Investigation, researchers led by Harvey Cantor at Harvard University analyzed the contributions of different subsets of T cells to an RA-like condition in mice. Cantor and colleagues identified a subset of regulatory T cells (CD8+ Tregs) that can remove pathogenic T cell subsets and inhibit disease progression. Additionally, they identified small proteins that induced more CD8+ Tregs. These findings suggest that enhancing specific T cell subsets may be useful in combating RA and other autoimmune diseases.