Primate Monocytes - CD14, CD16 - Ziegler-Heitbrock

Increased Toll-like receptor-2 expression on non-classical CD16+ monocytes from patients with inflammatory stage of Eales' disease

Abstract

Purpose: To identify the distribution, differential Toll-like receptor (TLR) expression and functional contribution of monocyte subpopulations in the inflammatory stage of Eales' disease (ED). Methods: Peripheral blood mononuclear cells were isolated from nine patients with inflammatory stage of ED and nine age and sex matched healthy controls. The expression of CD14, CD16, TLR-2 and TLR-4 on monocytes was measured by flow cytometric analysis. CD14+, CD16- and CD16+ monocyte population were sorted based on magnetic-activated cell sorting methodology and levels of cytokines was measured by ELISA. Results: In ED patients, the number of circulating monocytes were significantly expanded compared to controls (P = 0.01) with a marked increase of non-classical CD16+ subset, that showed an activated phenotype in patients, which correlated with levels of serum pro-inflammatory cytokines and clinical progression. A higher expression of cell surface TLR-2 (P = 0.02), but not TLR-4 was found in monocytes from patients with ED. Furthermore, TLR-2 was expressed at higher levels on CD16+ monocytes than CD16- monocytes in patients, while no significant variation was found in TLR-4 expression on different monocyte subsets. Peptidoglycan induced TNF-α expression was correlated with TLR-2 expression in monocytes isolated from controls (r = 0.85, P = 0.0061), but not in monocytes isolated from ED patients (r = 0.553, P = 0.1328). Conclusions: These results indicate that in the pathogenesis of ED, TLR-activation and increased numbers of non-classical CD16+ monocytes are crucial regulators, which is accompanied by secretion of pro-inflammatory cytokines that perpetuates the inflammatory process in the retina