Systemic levels of the T cell regulatory cytokines IL-10 and IL-12 in Bechçet's disease; soluble TNFR-75 as a biological marker of disease activity.

OBJECTIVE

To analyze the levels of the T cell regulatory cytokines interleukin 10 (IL-10) and IL-12 in plasma of patients with Behçet's disease (BD), and to assess the value of cytokines and cytokine antagonists as biological markers of disease activity.

METHODS

Sera/plasma of 66 consecutive outpatients with established diagnosis of BD were analyzed for the presence of IL-2R, IL-6, tumor necrosis factor-alpha (TNF-alpha), soluble (s) TNF receptor (R)-55, sTNFR-75, IL-10, and IL-12 using immunological methods. Additional laboratory measurements included erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). Data from the history and clinical examination were recorded to correlate cytokine levels with clinical markers of disease activity.

RESULTS

18 patients had inactive (Group I), 36 had mildly active (Group II), and 12 patients had active BD (Group III). IL-10 was elevated in 42 plasma samples (64%). The percentage of samples containing IL-10 and the median levels of IL-10 of the 3 patient groups did not differ significantly. IL-12 was detectable in plasma of 9 patients: One from Group I (5%), 3 from Group II (8%), and 5 from Group III (41%). IL-12 correlated with disease activity (difference between Groups I and III, p = 0.02, between Groups II and III, p = 0.008). ESR in patients with active disease and mildly active disease was significantly higher than values in patients with inactive disease (p = 0.03, p = 0.02, respectively), while median CRP levels were significantly different between Group I and Group III only (p = 0.006). sTNFR-75 levels were significantly different between Groups II and III (p = 0.003) and between Groups I and III (p = 0.008).

CONCLUSION

The elevation of plasma IL-10 in the majority of patients and the correlation of IL-12 plasma levels with disease activity suggest a pathogenic role of a TH1-type immune response in active disease. In addition, the correlation of sTNFR-75 levels with disease activity indicates that sTNFR-75 may serve as a biological marker of disease activity in BD.