Immune mechanisms in type-2 diabetic retinopathy.

Objective: To enumerate CDR+CD25+ Treg cells and determine serum IL-6 and IL-17 in type 2 diabetes mellitus patients with retinopathy.

Methods: The case-control study was conducted at the Department of Immunology, University of Health Sciences, Lahore, from November 2009 to January 2012 and comprised diabetic patients and healthy controls who were divided into three groups. Group 1 had controls, while Group 2 had diabetic patients without retinopathy and Group 3 had diabetic patients with retinopathy. Flowcytometre and enzyme-linked immunosorbent assay were used for CD4+CD25+ Tregs and serum IL-6 and IL-17 respectively. SPSS 20 was used for statistical analysis.

Results: Of the 212 subjects in the study, 30(14%) were Group 1, 30(14%) in Group 2 and 152(72%) in Group 3.There were 25 (83%) women in Group 2 and 101 (66%) in Group 3 compared to 9 (30%) in Group 1. Higher mean age was in Group 3 (50.88 ± 8.9 years) and Group 2 (49.46 ± 9.94 years) compared to Group 1 (34.66 ± 8.78 years) while longer mean disease duration was in Group 3 (10.51 ± 5.24 years) than Group 2 (7.76 ± 4.14 years). Highest median ratio of IL- 6 was in Group 1 (1468.62) (Q1-Q3: 1229.9-1543.35), followed by Group 2 (1455.32) (Q1-Q3:1214.22-158.9) and Group 3 (469.84) (Q1-Q3: 206.53-1231.33) whereas IL-17 was the highest in Group 1 (339.38) (QT-Q3: 159.89- 1174.93), followed by Group 3 (216.60) (Q1-Q3:141.87-410.25) and Group 2 (174.17) (Q1-Q3: 138.77-458.17). Higher percentage of Tregs was in Group 2 (3.07 ± 0.43) followed by Group 1 (2.91 ± 0.04) and Group 3 (2.88 ± 0.38). Significant difference was observed in gender, age, disease duration, level of IL-6 and IL-17 (p < 0.05 each), while no difference was found in glycated haemoglobin, CD4+CD25+ and Tregs (p > 0.05 each).

Conclusion: Age, gender and duration of diabetes contributed to diabetic retinopathy, while CD4+CD25+ T cells and Treg cells did not. Serum IL-6 and IL-17 were inversely associated with diabetic retinopathy.