The dynamic changes of regulatory T cells in the pathogenesis of experimental autoimmune uveitis

Background

Studies show that regulatory T cells (Treg) are a kind of T cell subsets to negatively regulate immune response, and play an important role in maintaining immune homeostasis and immune tolerance.Autoimmune uveitis is an autoimmune disease, the regulation of Treg cells in pathogenesis and progression of autoimmune uveitis is not fully unelucidated.

Objective

This study was to observe the dynamic changes of Treg in experimental autoimmune uveitis (EAU) rats and explore the role of Treg cells in the pathological process of EAU rats.

Methods

Eighty four 6-8 week-old SPF Lewis rats were randomly divided into model group and control group.The mixed emulsifier of interphotoreceptor retinoid-binding protein (IRBP)_1177-1191, tuberculin (TB), complete Freund adjuvant (CFA) and PBS (300 μl) was subcutaneously injected in double rear foot pad, abdominal side and back, and only equal amount of TB, CFA and PBS emulsifier was used in the same way in the control group.Ocular inflammation symptoms was examined at 9, 13, 18, 23, 28, 35 and 48 days after modeling and scored based on the severity of the inflammatory.Six rats of each group were sacrificed in above time points respectively for the histopathological examination of iris, ciliary body and retinas by haematoxylin-eosin staining.The lymphocytes were isolated and cultured from rat spleens, and the proportion of Foxp3-labelled cells, a specific marker of Treg cells, was assayed by flow cytometry.The relative expression level of Foxp3 mRNA in the lymphocytes detected by using real-time quantitative PCR (RT-PCR). The use and care of the rats complied with the ARVO Statement.

Results

Eye inflammatory response appeared at 8 days after immunization, showing vasodilation and hyperemia of rat iris in the model group, and the response peaked at 13 days, with exudation and hypopyon in the anterior chamber.The highest inflammatory scores were 3.75±0.42 at day 13, and the ocular inflammation reaction was gradually relieved after that and disappeared at 23 days after immunity.A significant difference in ocular inflammatory scores of model rats was found among different time points (F=81.709, P<0.001); while no inflammatory symptom was observed in the control group.Histopathology examination showed obvious infiltration of inflammatory cells in the iris, ciliary body and retinas in model rats, including neutrophils, lymphocytes and mononuclear cells.The proportion of Foxp3-labelled cells in spleen lymphocytes was (5.50 ± 0.64)%, (13.36 ± 0.98)%, (10.34 ± 0.79)%, (9.58 ± 1.02)%, (6.73 ± 0.81)% and (5.58 ± 0.47)% in the model group on day 13, 18, 23, 28, 35, 48 respectively, with statistically significant differences in comparison with (2.80±0.38)%, (3.36±0.53)%, (3.65±0.57)%, (3.37±0.43)%, (3.33±0.50)% and (3.13±0.61)% in the control group (t=-6.272, -15.556, -11.910, -9.753, -6.154, -5.491, all at P<0.01). The change trend of Foxp3 mRNA expression was consistent to the dynamic change of the proportion of Foxp3-labelled cells.

Conclusions

The pathogenesis and development is closely associated with the dynamic changes of CD4⁺ CD25⁺Foxp3⁺ Treg cells in EAU rats.

Uveitis, autoimmune, experimental/immunology; T-lymphocytes, regulatory/immunology; Lymphocyte activation; Rats, inbred Lew; Disease models, animal; Forkhead transcription factors/immunology; Spleen/immunology