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Soumyava Basu, Ravi Chandra Tagirasa, Manas Ranjan Barik, Satish Devadas; Phenotypic and functional characterization of intraocular T cell response in intraocular tuberculosis. Invest. Ophthalmol. Vis. Sci. 201657(12):.
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© ARVO (1962-2015); The Authors (2016-present)
The etiopathogenesis of intraocular tuberculosis (TB) has remained controversial due to its multiple clinical presentations and lack of definitive evidence of Mycobacterium tuberculosis (Mtb) in ocular samples. Our study explores the phenotypic and functional characteristics of T cells in clinically diagnosed intraocular TB to understand the pathogenetic mechanisms of the disease.
Vitreous samples (undiluted and diluted) and venous blood (5 mL) were collected from clinically diagnosed intraocular TB (based on clinical signs, ancillary tests and exclusion of non-TB uveitis) and control (confirmed non-TB uveitis) patients. 50μL of undiluted vitreous was used for Mtb PCR. T cells were recovered from remaining vitreous and blood sample by standard techniques, and activated with PMA-ionomycin and additionally Mtb-specific peptide ESAT-6, whenever adequate T cells were available in a given sample. Flow cytometric analysis was done for surface markers CD4, CD8, CD45RA and CD45RO. Intracellular cytokine staining was done for IFNγ, IL17, TNFα and IL10.
19 samples of intraocular TB and 5 non-TB controls were studied. Majority of cases (n=14) had retinal vasculitis. 12 cases (63.2%) were PCR-positive for Mtb. Phenotypic analysis of intraocular TB samples revealed predominance (>80%) of CD4+ cells, mainly from CD45RA-RO+ effector memory compartment. IFNγ and TNFα positivity was seen in all samples, while triple positive (IFNγ, IL17, TNFα) cells were seen in 7 of 19 samples. Mtb-antigen specificity was noted in 4 of 4 tested intraocular TB samples.
T cell response in intraocular TB is characterized by predominant presence of effector memory CD4+ cells, that suggests the role of past infection in pathogenesis of the disease. These T cells are highly pro-inflammatory and can include both Th1 and Th17 subsets. We demonstrate for the first time involvement of Mtb-specific T cells in intraocular TB.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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