Serum soluble interleukin 6 (IL-6) receptor and IL-6/soluble IL-6 receptor complex in systemic juvenile rheumatoid arthritis

J Clin Invest. 1994 May;93(5):2114-9. doi: 10.1172/JCI117206.

Abstract

By using a sandwich ELISA, soluble human IL-6 receptor (sIL-6 R) levels were measured in the sera of 20 healthy children and of 25 patients with systemic juvenile rheumatoid arthritis (JRA). In patients with systemic JRA, serum sIL-6 R levels (114.6 +/- 37.7 ng/ml) were significantly lower (P < 0.01) than those of healthy children (161.2 +/- 45.5 ng/ml). Serum sIL-6 R levels were negatively correlated (r = -0.610, P < 0.001) with serum IL-6 levels measured with the B9 cells. The serum IL-6/sIL-6 R complex was detected using an ELISA based on a monoclonal antibody to IL-6 for capture and on a monoclonal antibody to human sIL-6 R for detection. Healthy controls had little, if any, detectable serum IL-6/sIL-6 R complex (OD 0.024 +/- 0.027), while the majority of patients with systemic JRA presented measurable serum IL-6/sIL-6 R complex (OD 0.492 +/- 0.546). IL-6 levels estimated in the circulating IL-6/sIL-6 R complexes were in the range of nanograms per milliliter and approximately 20-fold higher than those measured by the B9 cells. Since serum C-reactive protein concentrations were much more correlated with serum levels of IL-6/sIL-6 R complexes (r = 0.713, r2 = 0.51, P < 0.0001) than with the serum IL-6 levels measured with the B9 cells (r = 0.435, r2 = 0.19, P = 0.05), the large quantities of serum IL-6 present in IL-6/sIL-6 R complexes appear to be biologically relevant in vivo, at least as far as the induction by IL-6 of acute phase protein production.

MeSH terms

  • Adolescent
  • Arthritis, Juvenile / blood*
  • Arthritis, Juvenile / classification
  • Arthritis, Juvenile / etiology
  • Child
  • Child, Preschool
  • Enzyme-Linked Immunosorbent Assay / methods
  • Humans
  • Interleukin-6 / isolation & purification*
  • Interleukin-6 / metabolism
  • Macromolecular Substances
  • Protein Binding
  • Receptors, Interleukin / isolation & purification*
  • Receptors, Interleukin / metabolism
  • Receptors, Interleukin-6
  • Solubility

Substances

  • Interleukin-6
  • Macromolecular Substances
  • Receptors, Interleukin
  • Receptors, Interleukin-6