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A.M. Hayden, F.N. Ross–Cisneros, D.T. Nguyen, W.R. Freeman, A.A. Sadun; An Immunohistochemical (IHC) Examination of Tumor Necrosis Factor (TNF–) Presence in the Optic Nerves of Patients With Chronic HIV Infection . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1085.
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To determine if TNFα is present in optic nerves from patients chronically infected with HIV.
28 retrobulbar optic nerves were collected at autopsy from 14 patients previously established to have chronic HIV infection. One age matched control retrobulbar optic nerve was also collected. The nerves were immersion–fixed in 10% formalin. 3mm cross–sections of the nerves were embedded into paraffin and then cut on a microtome at 4µ. A two–step indirect IHC staining method was employed using an HRP–conjugated secondary antibody reacting with a DAB substrate–chromogen system. The Primary Antibody directed against human TNF–α was diluted to 1:250. The slides were analyzed using a Zeiss Axioskop light microscope. The optic nerve’s IHC staining was graded on a scale from 0 to 4. 0 staining appeared to have none, or very trace evidence of DAB+ staining within the optic nerve tissue and the surrounding dura. A 4 appeared to have specific, heavy staining throughout the optic nerve.
We examined 28 nerves from 14 HIV. 5 of the 28 nerves had a grade 4 positive staining. Positive staining for TNF–α appeared most evident in the cytoplasm and nuclei of endothelial cells, the cytoplasm of supportive neural cells, and light staining within the axons themselves. Another 13 nerves appeared to have grade 2 and 3 staining within the optic nerve. This staining was most commonly scattered throughout the neural tissue and appeared to stain axons and supportive neural cells. Lastly, the remaining 10 nerves were observed to have minimal staining, considered a 1 on the established scale. However, only the normal age matched control was considered to have trace staining, or a grade of 0.
The central nervous system (CNS) of HIV positive patients express TNF–α in affected but not necessarily infected cells. This study is the largest examination of TNF α in optic nerves from patients with HIV and shows not only significant presence of TNFα but also a gradient of TNF–α expression. Optic nerves also suffer from inflammation and degeneration due to chronic exposure to TNF–α from macrocytes activated by HIV.
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