TNFSF13B and cryoglobulinemia: Ultimately, a recently discovered cytokine belonging to the TNF family, B-cell activating factor (BAFF), would seem to play an essential role in the maturation, proliferation, and clonal expansion of B lymphocytes; the detection of high serum levels of BAFF in patients with LES, AR, SS, and chronic HCV infection strongly suggests the correlation between BAFF and HCV cryoglobulinemia.