Increased Frequency and FoxP3 Expression of Natural Regulatory T Cells in the Aqueous Humor of Uveitis Patients

Abstract

Purpose: : The influx of leukocytes into the anterior chamber in uveitis is characterized by a predominance of T lymphocytes which are assumed to play a role in the pathology of non-infectious uveitis. It is now clear that, in common with other autoimmune and inflammatory diseases, there is defective phenotype and function of natural regulatory Tcells (nTreg) from peripheral blood of uveitis patients. However, in this study we wished to determine whether there are alterations in the number, phenotype or function of nTreg in the aqueous humor (AqH) of uveitis patients.

Methods: : AqH and peripheral blood were obtained from acute non infectious uveitis patients, both untreated and those on topical glucocorticoid treatment. Multi-colour flow cytometry was performed on AqH cells and peripheral blood mononuclear cells (PBMC) from these patients using antibodies specific for CD4, CD45RO, CD69, FoxP3, CD127 (IL-7R), CD25 (IL-2R) and CD39. nTreg were defined as CD4⁺CD25^highCD127^low lymphocytes. nTreg isolated from control individuals were co-cultured with dexamethasone/TGFβ₂ or activated in vitro with CD3/CD28 coated beads.

Results: : The frequency and FoxP3 expression of nTreg in uveitis AqH were significantly increased compared to their peripheral blood counterparts. Increased FoxP3 expression correlated with increased CD25 expression in AqH nTreg. The AqH nTreg were all primed (CD45RO+). CD69, an early activation marker was not expressed by these nTreg indicating that the increased FoxP3 expression was not due to recent activation of conventional T cells. Interestingly the majority of the ocular nTreg were CD39+. In vitro activation of nTreg increased their FoxP3 expression to levels similar to that in the eye. TGFβ₂ or dexamethasone had no effect on FoxP3 expression.

Conclusions: : There is an increased frequency and elevated FoxP3 expression of nTreg in uveitis AqH. We are currently determining whether these nTreg are functionally active or if they are inhibited by the inflammatory intraocular microenvironment.

Keywords: immunomodulation/immunoregulation • uveitis-clinical/animal model • aqueous