Stimulation of the B9 hybridoma cell line by soluble interleukin-6 receptors.
Interleukin-6 (IL-6) exerts its effects by binding to specific receptors on the cell surface. The IL-6 receptor consists of at least two components, a ligand binding 80 kDa low-affinity component (IL-6R) and a signal-transducing non-ligand binding 130 kDa component (gp130). The presence of soluble forms of these components has been described in both conditioned media and biological fluids. The soluble (s) IL-6R has been shown to enhance the IL-6 sensitivity of several both murine and human IL-6 sensitive cell types. A sensitive and commonly used method for measuring biological IL-6 activity is based on the IL-6 dependent proliferation of the murine hybridoma cell line B9. In this paper, we demonstrate that recombinant (r) human (h) sIL-6R enhances the sensitivity of B9 cells in a dose-dependent manner. The rhsIL-6R enhanced the binding of 125I-rhIL-6 to B9 cells. The rhsIL-6R induced stimulation of B9 proliferation was maximal at 100 ng/ml, even without addition of rhIL-6 and in the presence of anti-hIL-6 antibodies. This may be due to endogenous IL-6 production by the B9 cells, low levels of IL-6 in the fetal calf serum used, or perhaps an IL-6 independent effect by the rhsIL-6R. In conclusion, this and other reports point to the necessity of confirming measured biological activities through the use of neutralizing specific antibodies or parallel measurements in immunochemical assays.
Diamant
M
M
Medical Department TTA 7544, Rigshospitalet, Copenhagen, Denmark.
Hansen
M B
MB
Rieneck
K
K
Svenson
M
M
Yasukawa
K
K
Bendtzen
K
K
D000818:Animals; D002460:Cell Line; D004306:Dose-Response Relationship, Immunologic; D004797:Enzyme-Linked Immunosorbent Assay; D006358:Hot Temperature; D006825:Hybridomas / Q000276:immunology*; D015850:Interleukin-6 / Q000276:immunology*; D008213:Lymphocyte Activation; D011817:Rabbits; D018123:Receptors, Interleukin / Q000276:immunology*; D019947:Receptors, Interleukin-6; D011994:Recombinant Proteins / Q000276:immunology
D015850:Interleukin-6; D018123:Receptors, Interleukin; D019947:Receptors, Interleukin-6; D011994:Recombinant Proteins