Natural killer cells in vernal keratoconjunctivitis.

PURPOSE Recent studies suggest that natural killer (NK) cells exert effector/regulatory properties on both innate and adaptive responses via release of different cytokines. While some information indicates NK cells in allergic asthma and atopic dermatitis, no data are available for allergic conjunctivitis. The aim of this study was to evaluate NK in the blood and the conjunctiva of patients with vernal keratoconjunctivitis (VKC). METHODS Six patients with active VKC and six healthy subjects were included in the study. Blood samples and conjunctival biopsies were taken from each patient. NK cells in blood and conjunctiva were quantified by flow cytometry and immunohistochemistry, respectively. Clinical findings of the patients were recorded, conjunctival immune infiltrates were characterized, and both parameters were correlated to NK cell number. RESULTS Compared to healthy subjects, NK cells were significantly decreased in the blood and increased in the conjunctiva of patients with VKC. CONCLUSIONS Together with lymphocytes, eosinophils, and mast cells, NK cells constitute a significant proportion of the immune cells infiltrating VKC conjunctiva. This finding indicates a potential role of NK and innate immunity in the regulation of allergic reactions and in diseases such as VKC. New therapeutic alternatives for modulating allergic inflammation might target NK cells.