Dendritic cells from uveitis patients have a mature phenotype and a reduced capacity to take up antigen

Abstract

Purpose: In experimental animal models of uveitis, specialized subsets of dendritic cells (DCs) have been shown to either induce or suppress inflammation in the eye. However, little is known about the phenotype and function of these DC subsets in the context of clinical uveitis in man. The purpose of this study was to characterize DCs in the peripheral blood of patients with uveitis, and also to assess their functional capacity to present antigen, secrete cytokines and induce T helper cell activation and proliferation.

Methods: Fresh peripheral blood from uveitis patients (n=92) and healthy controls (HCs, n=112), was analysed by flow cytometry. HLA-DR+ myeloid DC1 (mDC1), mDC2 and plasmacytoid DCs (pDC) were then identified by their BDCA-1, BDCA-3 and BDCA-2 expression. Monocyte-derived DCs (MoDCs) were also generated from uveitis patients and HCs by culturing isolated CD14+ cells for 6 days with GM-CSF and interleukin (IL)-4. The capacity of DCs to process antigen and respond to lipopolysaccharide (LPS) was then quantified by measuring FITC-labeled albumin uptake, intracellular cytokine expression and co-cultured CD4+ T cell activation.

Results: The mDC1 pool is expanded in the peripheral blood of uveitis patients both as a percentage of all DCs (p=0.007) and in terms of absolute numbers of cells (p=0.012), whereas the absolute number of mDC2 and pDCs was unchanged compared with HCs. This expansion was independent of the diagnostic category of uveitis (either by disease description or anatomical classification) and treatment. However, the intensity of HLA-DR expression was increased in mDC1 cells from patients with uveitis (p=0.02), and this increase was most pronounced in patients in disease remission (p=0.01). Myeloid DC1 cells from uveitis patients also had a greater capacity to upregulate HLA-DR in response to LPS (p=0.005), but their upregulation of IL-6, IL-10 and IL-12p40/70 expression was reduced compared with HCs. Antigen uptake was also decreased in mDC1 cells from uveitis patients (p=0.01). Albumin(low) MoDCs from HCs induced greater CD4+ cell activation in T-cell co-cultures.

Conclusions: DCs in the peripheral blood of uveitis patients are skewed to a mature, HLA-DR(high) mDC1 phenotype, with a reduced capacity for antigen uptake, and exhibit a blunted upregulation of IL-6, IL-10 and IL-12p40/70 following LPS stimulation.

Keywords: 555 immunomodulation/immunoregulation • 746 uveitis-clinical/animal model • 490 cytokines/chemokines