Aims: The vitreous levels of soluble intercellular adhesion molecule 1 (sICAM-1) were investigated in uveitic eyes undergoing vitrectomy for retinal detachment (RD) or other complications, and the presence of this molecule was related to disease activity and vitreous levels of the cytokine tumour necrosis factor alpha (TNF alpha), known to upregulate ICAM-1 expression on various cells.
Methods: Vitreous and serum samples from 23 patients with either active or quiescent uveitis undergoing retinal surgery were examined for the levels of immunoreactive sICAM-1 and TNF alpha by ELISA methods, and for the presence of biologically active TNF alpha. Vitreous from non-uveitic eyes with rhegmatogenous retinal detachment (RRD), macular holes or cadaveric eyes were used as controls.
Results: As a whole, vitreous from uveitic eyes complicated or uncomplicated by RRD contained significantly higher levels of sICAM-1 than vitreous from non-uveitic eyes with RRD alone (p < 0.0005), eyes with macular holes (p < 0.0001), or normal cadaveric vitreous (p < 0.0001). The proportion of vitreous containing > 20 ng/ml sICAM-1 (> four times the normal values) was significantly higher in eyes with uveitis complicated by RRD than in those eyes without RRD (Fisher's test, p = 0.02), and although levels of sICAM-1 were higher in eyes with active uveitis than in those with quiet disease (p < 0.02), this could not be dissociated from the increase caused by RRD. There was a relation between the vitreous levels of sICAM-1 and those of immunoreactive TNF alpha (Spearman's correlation coefficient; r = 0.601, p = 0.006), but not between the vitreous levels of sICAM-1 and those of biologically active TNF alpha.
Conclusion: Increased vitreous sICAM-1 levels and the association of this molecule with the presence of immunoreactive TNF alpha in uveitic eyes confirm the operation of cytokine mediated vascular reactions at the blood-retinal barrier during the development of this condition. The persistence of high vitreous levels of sICAM-1 in eyes with uveitis complicated by RRD despite previous immunosuppression may indicate a low rate of clearance of inflammatory molecules from the vitreous cavity and an exacerbation of the existing inflammatory process by the retinal detachment itself.