Background: Oral lichen planus (OLP) is a T cell-mediated inflammatory disease. Interleukin-6 (IL-6) is a pro-inflammatory cytokine that has effects on cellular and humoral immunities. Previous studies have shown that keratinocytes and tissue-infiltrating mononuclear cells from OLP lesions can secrete IL-6. In some OLP patients, the high serum IL-6 levels are reduced after treatment, suggesting that IL-6 may be a useful marker in evaluating therapeutic effects and in monitoring the disease status of OLP.
Methods: In this study, we used a solid phase, two-site sequential chemiluminescent immunometric assay to determine the baseline serum levels of IL-6 in a group of 180 patients with erosive OLP (EOLP), nonerosive OLP (NEOLP), erythema multiforme (EM), traumatic ulcers (TU), oral submucous fibrosis (OSF), pemphigus vulgaris (PV), or Sjögren's syndrome (SS), and in 77 normal control subjects. Some OLP patients were treated with levamisole plus Chinese medicinal herbs or levamisole only for 0.5–5.5 months and their serum IL-6 levels were measured after treatment.
Results: We found that approximately 99% of the normal control subjects and the patients with EM, TU, or OSF had a normal serum IL-6 level less than 5.0 pg/ml. However, 15% (22/149) OLP patients, 15% (20/136) EOLP patients, 20% (5/25) major type EOLP patients, 14% (15/111) minor type EOLP patients, 15% (2/13) NEOLP patients, 14% (1/7) EM patients, 43% (3/7) PV patients, and 100% (6/6) SS patients had a serum IL-6 level greater than 5.0 pg/ml. The mean serum IL-6 level in patients with OLP (3.4 ± 3.1 pg/ml, P < 0.001), EOLP (3.4 ± 3.2 pg/ml, P < 0.001), major type EOLP (4.9 ± 3.5 pg/ml, P < 0.001), minor type EOLP (3.0 ± 3.0 pg/ml, P < 0.01), or NEOLP (4.2 ± 1.5 pg/ml, P < 0.001) was significantly higher than that in normal control subjects (2.0 ± 1.5 pg/ml). A significant difference in the mean serum IL-6 level was also found between major type and minor type EOLP patients (P < 0.01). The mean reduction of serum IL-6 level in OLP patients treated with levamisole plus Chinese medicinal herbs was significantly higher (7.4 ± 4.7 pg/ml) than that in OLP patients treated with levamisole only (3.8 ± 2.3 pg/ml, P < 0.05), suggesting that the combination therapy was superior to levamisole only.
Conclusion: We conclude that levamisole and levamisole plus Chinese medicinal herbs can modulate the serum IL-6 level in OLP patients. IL-6 may be a useful marker in evaluating therapeutic effects and in monitoring the disease status of OLP.