IL-6: from laboratory to bedside.

In the late 1960s, the essential role of T-cells in antibody production was reported. This suggested to us that certain molecules should be released from T-cells for the stimulation of B-cells. We discovered activities in the culture supernatant of T-cells that induced proliferation and differentiation of B-cells. The factor that induced B-cells to produce immunoglobulins was named B-cell stimulatory factor (BSF)-2. The complementary DNA that encoded human BSF- 2 was cloned in 1986. Simultaneously, interferon-beta2 and 26-kDa protein in the fibroblasts were independently cloned by different groups and were found to be identical to BSF-2. Later, a hybridoma/plasmacytoma growth factor and a hepatocyte-stimulating factor also were proven to be the same molecule as BSF-2. Various names were used for this molecule because of its multiple biological activities, and thereafter, these names were unified as interleukin (IL)-6. Since the discovery of IL-6, rapid progress has been made in understanding its actions, the IL-6 receptor system, and the IL-6 signal transduction mechanism. More importantly, it was involved in numerous diseases, such as rheumatoid arthritis and Castleman's disease. By accumulating the basic knowledge, a new therapeutic approach by blocking IL-6 actions appeared to be feasible for chronic inflammatory diseases.