Abstract
Birdshot Retinochoroiditis (BSRC) is a progressive non-infectious intraocular inflammation that affects choroid and retina. Inflammatory processes have adverse effects on vision by affecting photoreceptor-bearing cells that do not regenerate. This study aimed at characterizing inflammatory CD4+ and CD8+ T cell subsets in the peripheral blood of active and inactive BSRCs. Furthermore, we correlated phenotypical and functional immunological analyses with clinical data. We observed a slight increase of terminally differentiated effector memory CD8+ T cells expressing CD45RA (TEMRA) in blood of inactive, compared to active BSRCs. Moreover, we identified a trend for a decreased population of TH2 cells and increased TH1 frequencies in active BSRCs, a typical sign of ongoing autoimmune processes. Functional assays demonstrated severe and overall impairment of effector function of both, CD4+ and CD8+ inflammatory T cells, which might reflect T cell exhaustion. Although the eye is the main site of inflammation in BSRC, we observed altered T cell subset compositions in the peripheral blood, dependent on the disease status. Our results indicate that T cells may play a major role in BSRC pathology, although our cohort size is too limited for definitve conclusions. Future studies with larger BSRCs have to be performed.
Highlights
Birdshot Retinochoroiditis (BSRC) is a rare form of non-infectious posterior uveitis, in which recurrent inflammatory episodes affect retina and stromal choroid[1]
Kuiper and colleagues further strengthened this body of evidence by the discovery of certain polymorphisms in the endoplasmic reticulum aminopeptidase (ERAP) gene of BSRC patients leading to imbalanced ERAP 1 and 2 function, influencing peptide-presentation of human lymphocyte antigen (HLA)-A*29 to T c ells[7]
In line with these studies, T cells of BSRC patients produced IL-17 in response to human and choroid lysate and IL -17 secreting C D4+ and CD8+ T cells have been demonstrated to be enriched in the periphery of BSRC patients[21,22,23]
Summary
Birdshot Retinochoroiditis (BSRC) is a rare form of non-infectious posterior uveitis, in which recurrent inflammatory episodes affect retina and stromal choroid[1]. It was shown that the CD4+ T helper subset TH17 might be important to sustain chronic inflammation in various autoimmune diseases, such as psoriasis, inflammatory bowel disease, rheumatoid arthritis, and multiple sclerosis[17,18,19,20] In line with these studies, T cells of BSRC patients produced IL-17 in response to human and choroid lysate and IL -17 secreting C D4+ and CD8+ T cells have been demonstrated to be enriched in the periphery of BSRC patients[21,22,23]. Increased IL-17 and pro-inflammatory cytokines were presented in aqueous humor and serum of BSRC patients, suggesting IL-17 pathway activity[4,24] Most of these results were only noticeable in disease-active, treatment-naïve BSRC patients only. We correlated the resulting immunological phenotype with the clinical presentation of each BSRC patient on the sample collection day, intending to identify different immune signatures during clinical active or inactive state of disease
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