Abstract
Purpose: :
We have previously detected significantly increased levels of intracellular IL-4 expression within CD4+T cells derived from tear specimens in vernal kerato-conjunctivitis (VKC) suggesting a Th2-mediated effector T cell response. Cell-free tear specimens have also been found to include a range of proinflammatory cytokines including interferon-gamma and IL-4, but no detectable IL-17A. The aim of this study was to investigate the relative levels of Th2 T cells (CD4+ GATA-3+) and Th17 T cells (CD4+RORgt+) in tears-derived cells and levels of IL-17F in tears from patients with VKC and other subtypes of conjunctivitis.
Methods: :
Patients (tarsal VKC (VKC-T):n=10; limbal VKC (VKC-L): n=3; mixed VKC (VKC-M): n=8; controls: n=7) attending the Ophthalmology Unit at Padova University donated 5-20uL fresh tears’ fluids having obtained prior consent in accordance with the local Ethics’ committee. Cells were immediately isolated by centrifugation and fixed and cell-free supernatants stored frozen. Fixed cells were subsequently stained using anti-CD4, anti-RORgt, anti-GATA-3 mAbs and acquired for flow cytometric analysis. Th2 cells were defined as CD4+and GATA-3+ whilst Th17 cells were CD4+ and RORgt+. IL-17F detection was performed by ELISA.
Results: :
Increased levels of Th2 cells were detected in tears specimens from VKC-T (n=9; mean 20.2+/-6.7%) in comparison with tear specimens from other subtypes of conjunctivitis (n=7; mean 9.9+/-3.7%) although this did not reach significance. There was a negative correlation between GATA-3 expression and RORgt within the CD4+T cells in the VKC-T group (n=9; R2=-0.78). No correlations were observed within the total group of specimens, or within the other subtypes of conjunctivitis. Low levels of IL-17F were detected in 5 of the 15 tears fluids which did not correlate with detectable Th17 cells.
Conclusions: :
Variable levels of Th17 cells were detected in tears-derived cells in clinical subtypes of conjunctivitis. Intracellular coexpression of T cell subset-specific transcription factors has identified a predominance of Th2 T cells in VKC, which is inversely correlated with Th17 cells, suggesting VKC is mainly a Th2-driven response. The lack of correlation with IL-17F levels in tears fluids suggests these cells were not the source of this cytokine.
Keywords: conjunctivitis • cytokines/chemokines • inflammation