SOLUBLE INTERLEUKIN-6 RECEPTORS IN INFLAMMATORY BOWEL-DISEASE - RELATION TO CIRCULATING INTERLEUKIN-6

The in vivo appearance of soluble interleukin (IL)-6 receptor (sIL-6R) in serum from patients with inflammatory bowel disease was examined u sing an enzyme Linked immunosorbent assay (ELISA). The serum sIL-GR co ncentrations in patients with active disease (ulcerative colitis, 148. 4 (5.1); Crohn's disease, 142.3 (9.3) ng/ml; mean (SEM)) were signific antly raised compared with those in patients with inactive disease (ul cerative colitis, 116.2 (7.2); Crohn's disease, 114.3 (7.1) ng/ml), so me other type of colitis (104.8 (11.6) ng/ml), or in normal subjects ( 107.3 (2.4) ng/ml). These differences were also seen in paired samples examined during both active and inactive phases. Additionally, serum sIL-GR and IL-6 concentrations correlated significantly with C-reactiv e protein levels in both ulcerative colitis and Crohn's disease patien ts (r=0.23 and 0.56, respectively; p<0.05 for both). Furthermore, gel filtration analysis of serum from these patients showed two major peak s of immunoreactive IL-6 - one peak corresponding to free IL-6 and ano ther peak to sIL-6R-bound IL-6 - this was further confirmed by a lumin escence sandwich ELISA. These results, together with its in vitro effe cts, indicate that natural sIL-6R may function as a powerful enhancer of the IL-6-dependent immune processes observed in inflammatory bowel disease.