Concentration of Soluble Interleukin-6 Receptors in Tears of Allergic Conjunctival Disease Patients

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Abstract
To evaluate the significance of soluble interleukin-6 receptor (sIL-6R) in tears as a clinical indicator of disease exacerbation in patients with allergic conjunctivitis disease (ACD). The study groups comprised 13 patients (13 eyes) with vernal keratoconjunctivitis (VKC group), 13 patients (13 eyes) with atopic keratoconjunctivitis (AKC group), 11 patients (11 eyes) with giant papillary conjunctivitis (GPC group), and 10 healthy volunteers (10 eyes) as a control. Tear samples were collected by the Schirmer I method using filter paper. Tear samples were eluted and the concentration of sIL-6R in tear samples was determined by enzyme-linked immunosorbent assay. Impression cytology using a nitrocellulose membrane was applied to the upper tarsal conjunctiva, and the mRNA of the signal-transducing molecule glycoprotein 130 (gp130) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was extracted from the membrane and analyzed by semiquantitative reverse transcription-polymerase chain reaction. In the VKC group, the clinical score was graded on the basis of allergic inflammation of the ocular surface, and the correlation between the concentration of sIL-6R and the clinical score was studied. The concentration of sIL-6R in tears in the VKC, AKC, GPC, and control groups was 5.1 ± 4.7, 1.2 ± 1.7, 2.6 ± 2.8, and 0.5 ± 4.3 (mean ± SD) ng/ml, respectively. The concentrations of sIL-6R in tears in the VKC and GPC groups were significantly higher than those in the control group (P < 0.001 and 0.05, respectively). The AKC group showed no significant change in the concentration of sIL-6R in tears in comparison with the control group. The gp130/GAPDH mRNA ratio was significantly higher in the patients with ACD than in control individuals (P < 0.05). The concentration of sIL-6R in tears and the clinical score of allergic inflammation of the ocular surface were significantly correlated in the VKC group (r = 0.53, P < 0.01). We concluded that IL-6/sIL-6R complex trans-signaling via gp130 is an exacerbating factor of ACD, and that the concentration of sIL-6R in tears is a useful clinical biomarker in patients with ACD. Jpn J Ophthalmol 2007;51:332–337 © Japanese Ophthalmological Society 2007