Endogenous cortisol and TGF-beta in human aqueous humor contribute to ocular immune privilege by regulating dendritic cell function.

Aqueous humor (AqH) has been shown to have significant immunosuppressive effects on APCs in animal models. We wanted to establish whether, in humans, AqH can regulate dendritic cell (DC) function and to identify the dominant mechanism involved. Human AqH inhibited the capacity of human peripheral blood monocyte-derived DC to induce naive CD4(+) T cell proliferation and cytokine production in vitro, associated with a reduction in DC expression of the costimulatory molecule CD86. This was seen both for DC cultured under noninflammatory conditions (immature DC) and for DC stimulated by proinflammatory cytokines (mature DC). DC expression of MHC classes I/II and CD83 was reduced (mature DC only). Myeloid DC from peripheral blood were similarly sensitive to the effects of human AqH, but only under inflammatory conditions. The addition of α-melanocyte stimulating hormone and vasoactive intestinal peptide did not cause significant inhibition at physiological levels. However, the addition of exogenous cortisol at physiological levels recapitulated the AqH-induced reduction in CD86 and inhibition of DC-induced T cell proliferation, and blockade of cortisol in AqH partially reversed its suppressive effects. TGF-ß2 had an additional effect with cortisol, and although simultaneous blockade of cortisol and TGF-ß2 in AqH reduced its effectiveness, there was still a cortisol- and TGF-ß-independent component. In humans, AqH regulates DC maturation and function by the combined actions of cortisol and TGF-ß2, a pathway that is likely to contribute to the maintenance of immune privilege in the eye.

Clinical course and visual outcome in patients with diabetes mellitus and uveitis.

PURPOSE: We report the clinical course and visual outcome of patients with diabetes mellitus (DM) who subsequently developed uveitis from any cause. METHODS: Longitudinal, retrospective case note review. RESULTS: A total of 36 patients (M/F: 18/18, 58 eyes) were included, Of the 36 patients, 35 had Type 2 DM and one had Type 1 DM. Mean age of onset of DM was 49 years and uveitis 55 years. The uveitis was bilateral in 22 (61%) patients. There were 19 patients with anterior uveitis, 12 with panuveitis and 5 with intermediate uveitis. Mean follow up was 4.4 years (range 1-18). Mean number of uveitis recurrences was 3 (range 1-7). Causes of vision of 6/18 or worse appeared related to the uveitis in 9 eyes and diabetes in 4 eyes. Cataract occurred in 22 eyes, glaucoma in 17 eyes, and cystoid macular oedema in 10 eyes. Diabetic retinopathy was detected in 38 (65.5%) eyes (29 non-proliferative including 6 with clinically significant macular oedema, and 9 proliferative). Progression of diabetic retinopathy to proliferative stage occurred in 7 eyes of 4 patients over a mean duration of 4.4 years. In 10 patients with active uveitis the mean HbA1c was 80 mmol/mol [9.5%], (range 49-137 [6.6-14.7]), and 67 mmol/mol [8.3%] (range 46-105 [6.4-11.8]) when the uveitis was quiescent, p = 0.01. Better glycaemic control was required in 10 patients during episodes of uveitis. CONCLUSIONS: Patients with DM who develop uveitis may have a high complication rate, reduced vision and poor glycaemic control. Checking blood glucose during episodes of uveitis is important.

The dominant human conjunctival epithelial CD8αß+ T cell population is maintained with age but the number of CD4+ T cells increases.

The conjunctiva is a highly specialized ocular mucosal surface that, like other mucosa, houses a number of leukocyte populations. These leukocytes have been implicated in age-related inflammatory diseases such as dry-eye, but their phenotypic characteristics remain largely undetermined. Existing literature provides rudimentary data from predominantly immunohistochemical analyses of tissue sections, prohibiting detailed and longitudinal examination of these cells in health and disease. Using recovered cells from ocular surface impression cytology and flow cytometry, we examined the frequency of leukocyte subsets in human conjunctival epithelium and how this alters with age. Of the total CD45+ leukocyte population within the conjunctival epithelium, 87% [32-99] (median) [range] comprised lymphocytes, with 69% [47-90] identified as CD3 + CD56- T cells. In contrast to peripheral blood, the dominant conjunctival epithelial population was TCRαß + CD8αß + (80% [37-100]) with only 10% [0-56%] CD4+ cells. Whilst a significant increase in the CD4+ population was seen with age (r = 0.5; p < 0.01) the CD8+ population remained unchanged, resulting in an increase in the CD4:CD8 ratio (r = 0.5;p < 0.01). IFNγ expression was detectable in 18% [14-48] of conjunctival CD4+ T cells and this was significantly higher among older individuals (<35 years, 7[4-39] vs. >65 years, 43[20-145]; p < 0.05). The elevation of CD4+ cells highlights a potentially important age-related alteration in the conjunctival intra-epithelial leukocyte population, which may account for the vulnerability of the aging ocular surface to disease.

Aqueous humor suppression of dendritic cell function helps maintain immune regulation in the eye during human uveitis.

PURPOSE: Noninfectious uveitis is characterized by a dysregulated inflammatory or immune response in the eye. It is unclear whether this represents a failure of immune privilege or an overwhelming inflammatory drive that has exceeded the capacity of regulatory mechanisms that are still functioning. The authors investigated immune regulation in the human eye during intraocular inflammation (uveitis) and its impact on dendritic cell (DC) function and subsequent T-cell responses. METHODS: Myeloid DCs were isolated from the aqueous humor (AqH) and peripheral blood of patients with active uveitis and characterized by flow cytometry. The effect of uveitis AqH was interrogated in an in vitro model of peripheral blood monocyte-derived DCs from healthy controls. RESULTS: Myeloid DCs isolated from uveitic AqH were characterized by elevated major histocompatibility complex classes I and II (MHC I/II), but reduced CD86 compared with matched peripheral blood DCs. Exposure of peripheral blood monocyte-derived DCs from healthy controls to the inflammatory AqH supernatant recapitulated this phenotype. Despite interferon gamma (IFNγ)-dependent upregulation of MHC I, inflammatory AqH was overall suppressive to DC function, with reduced CD86 expression and diminished T-cell responses. This suppressive effect was equal to or greater than that induced by noninflammatory AqH, but was glucocorticoid independent (in contrast to noninflammatory AqH). CONCLUSIONS: These data indicate that the ocular microenvironment continues to regulate DC function during uveitis, despite IFNγ-driven upregulation of MHC expression, supporting the hypothesis that immune regulation within the eye is maintained during inflammation.

Clinical features of patients with diabetes mellitus presenting with their first episode of uveitis.

PURPOSE: Little is known about uveitis in patients with diabetes mellitus (DM). The authors studied diabetic patients with their first episode of uveitis. METHODS: Cross-sectional, case note study documenting the uveitis, underlying cause/syndrome, treatment, type of DM and treatment, and any diabetic retinopathy. RESULTS: There were 34 patients (M/F: 17/17, 48 eyes) with their first uveitis episode (33 had type 2 DM). Mean age of onset of DM 49 years and uveitis 56 years. Uveitis was bilateral in 14 (45%), with most having idiopathic anterior uveitis. Visual acuity 6/18-6/60 in 15 eyes, and worse than 6/60 in 11 eyes. There was 3-4+ flare in 16 eyes, 3-4+ anterior chamber cells in 13 eyes. Diabetic retinopathy was seen in 20 (42%) eyes, and mean blood glucose was 13.64 mmol/L in 11 patients. CONCLUSIONS: Diabetic patients presenting with uveitis, whatever the aetiology, may have severe inflammation, reduced vision, and poor glycaemic control.