TNFSF13B and rheumatoid arthritis: Markers of B-cell activation, such as beta2-microglobulin, immunoglobulin levels, free light chains (FLCs) of immunoglobulins, and BAFF (B-cell activating factor of the tumor necrosis factor [TNF] family) – which are all elevated in established RA [7-10] – could be useful in determining the extent of B-cell activation in early RA.