A similar low level expression of CD19 on long-lived plasma cell precursors has been described in peripheral blood from patients with primary Sjögren’s syndrome, rheumatoid arthritis and active systemic lupus erythematosus [38-40], and downregulation of CD19 expression during differentiation into antibody-secreting cells has been documented [41,42]. Here, CD19 is linked to rheumatoid arthritis.