Release of the soluble interleukin-6 receptor from human T-cells.

The soluble Interleukin-6 receptor (sIL-6R) is capable of conferring the Interleukin-6 (IL-6) signal onto cells lacking the gp80 ligand binding protein. Here we investigate the release of sIL-6R from T-cells. After 2 h stimulation with PMA, a release of sIL-6R from peripheral human T-cells was observed which was insensitive to the protein synthesis inhibitor cycloheximide. This release was accompanied by a decrease of membrane-bound (mb) IL-6R. After 24 h, however, the observed sIL6-R release did prove to be sensitive to cycloheximide. These results suggest that both shedding and denovo-synthesis may be responsible for the PMA-induced sIL-6R release. In contrast to PMA, neither anti-CD3, a positive, nor IL-10, a negative regulator of IL-6 release from T-cells affected the production of the sIL-6R. The differential regulation of sIL-6R and IL-6 production by T-cells might be relevant for the immunomodulatory potential of the sIL-6R with respect to the interaction of T- and non-T-cells.