Alterations in Circulating Leukocyte Populations in Diabetic Retinopathy

Abstract

Purpose : Diabetic retinopathy (DR) is the highest cause of blindness in the global working population. Inflammation is highly implicated in DR pathogenesis although the underlying mechanism remains poorly-defined. The aim of this study was to investigate the immunophenotype of circulating leukocytes in DR patients.

Methods : Peripheral whole blood was collected from 13 healthy controls (age-, gender-matched) and 39 type 1 DR patients, including 13 mild non-proliferative DR (NPDR), 14 non-active PDR (naPDR) and 12 active PDR (aPDR). Immunophenotype was examined by flow cytometry. The immune markers investigated in this study include lymphocytes (CD4 and CD8 T cells, CD19 B cells), monocytes (CD14⁺⁺CD16^-, CD14⁺⁺CD16⁺ and CD14⁺CD16⁺⁺); neutrophils (CD16⁺HLA-DR^-) and NK cells (CD56); chemokine receptor expression (CCR2 and CCR5); cell adhesion molecules (CD66a and CD157); inhibitory molecule (CD305); angiogenesis marker (TIE2) and cell activation markers (HLA-DR, CD62L).

Results : The percentages of lymphocytes (CD4⁺, CD8⁺, CD19⁺), non-classical monocytes (CD14⁺CD16⁺⁺), and HLA-DR⁺ cells were significantly reduced, and the percentage of neutrophils (CD16^hiHLADR^-) was significantly increased in DR compared to those in healthy controls. CD4⁺ cells from DR patients also expressed significantly lower levels of CD66a and CD157. The neutrophil-lymphocyte ratio (NLR), in particular, the CD16^hiHLADR^-/CD4⁺ and CD16^hiHLADR^-/CD19⁺ ratio was significantly higher in DR compared to that in healthy controls. The reduction in CD4 and CD8 T cells and the increment in CD16^hiHLADR^- neutrophils appear to be associated with the severity of DR, i.e., the orders of CD4% and CD8% T cells were aPDR<NPDR<Control, and the percentage of CD16^hiHLADR^- neutrophils was aPDR>NPDR>Control. There were no significant differences between the percentages of classical (CD14⁺⁺CD16^-) and intermediate (CD14⁺⁺CD16⁺) monocytes as well as populations positive for CD56, CCR2, CCR5, CD66a, CD305, TIE2 and CD62L between DR and controls.

Conclusions : Our results suggest that DR in type-1 diabetes may be related to increased innate immunity and reduced adaptive immunity and the neutrophil/CD4 ratio may be a useful marker to predict the severity or progression of DR. Further understanding the functional alterations of the immune cells may uncover the immune mechanisms of DR and identify potential targets for therapy.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.