Purchase this article with an account.
Hossein Nazari Khanamiri, Minhee Ko, Sindhu Saraswathy, Petros C. Karakousis, Narsing A. Rao; Phagocytosis and Replication of Mycobacterium Tuberculosis in Retinal Pigment Epithelium. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2782.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Histopathological evidence suggests a preferential localization of Mycobacterium tuberculosis (Mtb) in retinal pigment epithelium (RPE) and these cells express Toll-like receptors (TLR) and complement virtually identical to alveolar macrophages. This study aims to evaluate harboring of Mycobacteria in RPE compared to macrophages.
Human fetal RPE and THP-1 monocytes were cultured in vitro. The non-virulent Mtb strain H37Ra was grown to mid-log phase and used to infect each cell type with a cell: mycobacterium ratio (multiplicity of infection [MOI]) of 1:1 and 1:5. Non-phagocytosed mycobacteria were washed from culture plates after 12 hours of exposure (day 0). Cells were harvested at days 0, 1, and 5 for mycobacterial culture and calculation of colony-forming units (CFU). Expression of TLRs and complements was determined by polymerase chain reaction and immunohistochemistry.
At day 0, an equal number of Mtb was observed per THP-1 and RPE cell (0.3 and 0.4 Mtb per RPE and macrophage, respectively-MOI 1:5). At days 1 and 5, the CFU number was higher per THP-1 cell compared to RPE cells. With a MOI 1:5, the CFU count was 0.9±0.04 and 2.2±0.1 per RPE and THP-1 cell, respectively (p=0.003) at day 1. Also, with a MOI 1:5, the CFU count was 1.9±0.03 and 3.3±0.01 per RPE and THP-1 cell, respectively (p<0.001) at day5. Faster bacillary growth in THP-1 cells was associated with more cell death compared to RPE (17% live THP-1 cells versus 48% live RPE cells at day 5 with MOI 1:5).
The mycobacteria were readily phagocytosed by RPE similar to macrophages. However, mycobacteria replication in RPE is less and these cells survive more so compared to macrophages. These results suggest that the mycobacteria can be harbored in RPE without altering survival of these cells and the organisms can stay dormant in such cells.
This PDF is available to Subscribers Only