Abstract
We specify the clinical features of a spontaneous experimental autoimmune uveitis (EAU) model, in which foreign hen-egg lysozyme (HEL) is expressed in the retina, controlled by the promoter for interphotoreceptor retinol binding protein (IRBP). We previously reported 100% P21 (post-partum day) IRBP:HEL single transgenic (sTg) mice, when crossed to transgenic T cell receptor mice (3A9) generating the double transgenic (dTg) genotype, develop EAU despite profound lymphopenia (thymic HEL-specific T cell deletion). In this work, we characterized the immune component of this model and found conventional dTg CD4+ T cells were less anergic than those from 3A9 controls. Furthermore, prior in vitro HEL-activation of 3A9 anergic T cells (Tan) rendered them uveitogenic upon adoptive transfer (Tx) to sTg mice, while antigen-experienced (AgX, dTg), but not naïve (3A9) T cells halted disease in P21 dTg mice. Flow cytometric analysis of the AgX cells elucidated the underlying pathology: FoxP3+CD25hiCD4+ T regulatory cells (Treg) comprised ∼18%, while FR4+CD73+FoxP3-CD25lo/–CD4+ Tan comprised ∼1.2% of total cells. Further Treg-enrichment (∼80%) of the AgX population indicated FoxP3+CD25hiCD4+ Treg played a key role in EAU-suppression while FoxP3-CD25lo/–CD4+ T cells did not. Here we present the novel concept of dual immunological tolerance where spontaneous EAU is due to escape from anergy with consequent failure of Treg induction and subsequent imbalance in the [Treg:Teffector] cell ratio. The reduced numbers of Tan, normally sustaining Treg to prevent autoimmunity, are the trigger for disease, while immune homeostasis can be restored by supplementation with AgX, but not naïve, antigen-specific Treg.
Highlights
The relative contribution of T cell anergy (Tan) vs. regulatory T cells (Treg) in the context of autoimmunity has become blurred as a result of recent studies in evaluating the relationship between T regulatory cells (Treg) and Tan [1]
Transgenic interphotoreceptor retinol binding protein (IRBP):hen-egg lysozyme (HEL) mice were used to investigate in detail the clinical dynamics and severity of spontaneous autoimmune uveitis (EAU) in the double transgenic (dTg) genotype, using in vivo and in vitro methodological approaches, including the therapeutic adoptive transfer of an enriched Treg cell population
Since we have found that both limited anergy and lack of Treg potentially contributed to development of experimental autoimmune uveitis (EAU) in dTg mice, we explored the phenotype of these T cell populations at a single time point (P33) when EAU severity is approaching peak levels (Figure 1)
Summary
The relative contribution of T cell anergy (Tan) vs. regulatory T cells (Treg) in the context of autoimmunity has become blurred as a result of recent studies in evaluating the relationship between Treg and Tan [1]. This has particular relevance to the development of customized cell therapies for immune-mediated diseases, some of which are close to clinical translation. EAU is induced by subcutaneous inoculation of retina-specific antigens [9] in complete Freund’s adjuvant (CFA) Such conventional models may not be representative of “non-infectious” human uveitis, which develops in the absence of an obvious trigger, i.e., spontaneously [7]
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