The human interferon-beta 2 gene (IFNB2) product is identical to that for the B-cell stimulation factor-2 (BSF-2), the hybridoma growth factor (HGF) ("interleukin-6"), and the hepatocyte stimulating factor (HSF). Proteins derived from this gene mediate the plasma protein response to tissue injury (acute-phase response) and regulate the growth and differentiation of both B and T cells. Interleukin-6 (IL6) has come to be regarded as a potential osteoporotic factor because it has stimulatory effects on cells of the osteoclast lineage, and, thus, may play a role in the pathogenesis of bone loss associated with estrogen deficiency. IL-6 has many roles essential to the regulation of the immune response, hematopoiesis, and bone resorption. It is involved not only in the hepatic acute phase response but also in adipose tissue metabolism, lipoprotein lipase activity, and hepatic triglyceride secretion. Overproduction of IL-6, a proinflammatory cytokine, is associated with a spectrum of age-related conditions including cardiovascular disease, osteoporosis, arthritis, type 2 diabetes, certain cancers, periodontal disease, frailty, and functional decline. BSF-2 is a novel interleukin consisting of 184 amino acids.6 The standard product used in this kit is recombinant human IL-6, consisting of 184 amino acids with the molecular mass of 20.3kDa.