Circulating soluble interleukin-2 receptor alpha and beta chain in inflammatory bowel disease

Inflammatory bowel disease is characterized by T cell activation. Activated T cells shed interleukin-2 receptors (IL-2R) in a soluble form. A positive correlation between sIL-2R alpha (CD25) and disease activity in inflammatory bowel disease has been shown previously, whereas IL-2R beta (CD122) has never before been investigated in this respect. Serum from 27 patients with ulcerative colitis (UC), 31 with Crohn's disease (CD), and 29 healthy volunteers was obtained.

Disease activity was scored according to a semiquantitative score for UC and by Crohn's disease activity index for CD. sIL-2R alpha and -beta chains were assessed by a sandwich ELISA technique using monoclonal antibodies specific for CD25 and CD122, respectively.

The median concentration of sIL-2R alpha was 4424 pg/ml in healthy controls, 6460 in UC (p < 0.004), and 6371 in CD (p < 0.01). The corresponding value of sIL-2R beta in healthy volunteers was 605 pg/ml; in active UC, significantly lower levels were found at 233 pg/ml (p < 0.01), whereas in inactive UC, no such difference was observed at 725 pg/ml (p > 0.05). In CD, the levels were 839 pg/ml in inactive and 920 pg/ml in active disease stages (p > 0.05 vs controls). A positive and significant correlation existed between sIL-2R levels of alpha and beta chains in CD (r = 0.64; p < 0.01) but not in UC (r = -0.32; p > 0.05) or in healthy volunteers (r = 0.16; p > 0.05).

Future longitudinal studies will be necessary to learn whether this newly assessed sIL-2R beta (CD122), which may interfere with IL-15R, could be used to predict disease exacerbation and to monitor anti-inflammatory therapy in UC.