Expression of human beta-defensins in intraocular tissues

PURPOSE. Defensins are naturally occurring antimicrobial peptides. Recently the authors published evidence of defensin production by the human ocular surface. A study was undertaken to look for intraocular defensins that may account for unexplained antimicrobial activity of intraocular fluids. METHODS. Reverse transcription-polymerase chain reaction (RT-PCR) was perfo rmed on human postmortem ciliary body samples for beta defensins-1 (HBD-1) and beta defensin-2 (HBD-2), and alpha defensins 5 and 6. Induction of defe nsins by cytokines was analyzed in cultured human ciliary body epithelial ( CBE) and retinal pigment epithelial (RPE) cells. Polyclonal antibodies were used to immunoblot aqueous and vitreous to detect HBD-1 and HBD-2 and to e stimate their concentration. RESULTS. RT-PCR revealed constitutive HBD-1 message in ciliary body. HBD-2 and alpha defensin 5 and 6 messages were absent. HBD-2 message was induced by cytokine stimulation of both CBE and RPE cells. Immunoblots of vitreous and aqueous stained positively for HBD-1 but not HBD-2. The estimated aqueo us concentration of HBD-1 was less than 16 ng/ml. CONCLUSIONS. This Study demonstrates that HBD-1 is constitutively present i n the aqueous and vitreous. probably at sub-bacteriocidal concentrations. H BD-2, was absent from aqueous, but cytokine stimulation studies suggest tha t it may be generated in response to inflammatory cytokines during infectio ns. HBD-2 has a wider antibacterial spectrum, is 10-fold more potent, and m ay play a more significant role in antimicrobial defense than HBD-1. The us e of defensins therapeutically may be indicated; however, caution is requir ed because defensins also promote cell proliferation and fibrin formation, which are 2 key elements in ocular scarring processes such as proliferative vitreoretinopathy.