Tear levels of interferon‐γ, interleukin (IL) ‐2, IL‐4 and IL‐5 in patients with vernal keratoconjunctivitis, atopic keratoconjunctivitis and allergic conjunctivitis

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Abstract
A predominance of TH2 activity in chronic allergic diseases, such as vernal keratoconjunctivitis (VKC) and atopic keratoconjunctivitis (AKC), has been suggested recently. However, there is no published study on tear levels of cytokines of the two different subgroups, TH1 and TH2, in patients with ocular allergy. We measured interferon (IFN)-γ, interleukin (IL)-2, IL-4 and IL-5 levels in tears by ELISA, to determine whether the levels of these cytokines are elevated in allergic ocular diseases when compared among patient groups and normal controls. Tear levels of IL-2, IFNγ, IL-4 and IL-5 were measured by ELISA using samples from patients with VKC, AKC (AKC-NP, without proliferative lesions; and AKC-P, with proliferative lesions), allergic conjunctivitis (AC) and normal subjects. The levels of these cytokines in tears and the clinical severity of AD were also compared. Tear IL-4 level in patients with AKC was significantly higher than those in VKC, AC and controls, and tear IL-4 levels in patients with AKC-P vs VKC differed significantly. Tear IL-5 levels in patients with diseases associated with proliferative lesions, VKC and AKC-P, were higher than those in AC and normal controls. However, tear level of IL-5 in patients with AKC-P was significantly higher than that in AKC-NP. Although the dermatological severity of AD correlated significantly with tear IL-4 level, IFNγ, IL-2 and IL-5 levels did not correlate with dermatological severity of AD. These results indicate that the TH2-like cytokines play an important pathophysiological role in severe ocular allergic conditions such as AKC and VKC and that tear level of IL-5 may be a candidate marker to evaluate the clinical status of ocular allergy. The different patterns of tear levels of IL-4 and IL-5 among ocular allergic diseases may reflect the origin and immunological basis of these cytokines.