title: Subnormal cytokine profile in the tear fluid of keratoconus patients.
abstract: Keratoconus, historically viewed as a non-inflammatory disease, is an ectatic corneal disorder associated with progressive thinning of the corneal stroma. Recently, a few inflammatory mediators have been reported to be elevated in the tear fluid of keratoconus patients. Consequently, we investigated a wide range of inflammation regulating cytokines in the tears and sera of keratoconus and control subjects. Interleukin (IL)-1β, IL-4, IL-6, IL-10, IL-12, IL-13, IL-17, interferon (IFN)-γ, chemokine C-C motif ligand 5 (CCL5) and tumor necrosis factor (TNF)-α were tested in tear samples and sera of keratoconus and control individuals by multiplex immuno-bead assays. Selected cytokines were further tested by standard ELISA on pooled tear samples. All cytokines in the sera were generally low, with no significant changes between keratoconus and control subjects. However, in tear fluids, clear differences were detected between the two groups. These differences include increased IL-6, and decreased IL-12, TNF-α, IFN-γ, IL-4, IL-13 and CCL5 in keratoconus compared to control tear fluids. The decreases in IL-12, TNF-α and CCL5 were statistically significant, while the IL-13 decrease was statistically significant in the severe keratoconus group only. IL-17 could not be detected by multiplex immuno-bead assay, but showed an increase in keratoconus by conventional ELISA on a limited number of pooled tear samples. Our findings confirm increased IL-6, but dispute earlier reports of increased TNF-α, and suggest a cytokine imbalance in keratoconus disrupting corneal homeostasis. Moreover, an increase in IL-17 suggests tissue degenerative processes at work, contributing to the thinning and weakening of the corneal connective tissue in keratoconus.
authors.affiliation: Department of Ophthalmology, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Albert S
authors.initials: AS
authors.lastname: Jun
authors.forename: Leslie
authors.initials: L
authors.lastname: Cope
authors.forename: Caroline
authors.initials: C
authors.lastname: Speck
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Feng
authors.forename: Seakwoo
authors.initials: S
authors.lastname: Lee
authors.forename: Huan
authors.initials: H
authors.lastname: Meng
authors.forename: Abdel
authors.initials: A
authors.lastname: Hamad
authors.forename: Shukti
authors.initials: S
authors.lastname: Chakravarti
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D003315:Cornea / Q000502:physiology; D016207:Cytokines / Q000032:analysis* / Q000097:blood / Q000276:immunology; D005260:Female; D006706:Homeostasis / Q000276:immunology; D006801:Humans; D018836:Inflammation Mediators; D020381:Interleukin-17 / Q000032:analysis; D007640:Keratoconus / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D013666:Tears / Q000737:chemistry* / Q000276:immunology; D055815:Young Adult
chemical_list: D016207:Cytokines; D018836:Inflammation Mediators; D020381:Interleukin-17