Among disease controls, patients with osteoarthritis (n = 15) displayed a higher percentage of GM-CSF+ B cells (2.2 ± 1.0%) compared to patients with a non-RA inflammatory arthritis (PsA, n = 10, 0.9 ± 0.2%) or systemic inflammatory rheumatic diseases (n = 8, 1.5 ± 0.7%). Here, CSF2 is linked to rheumatoid arthritis.