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Samantha Dando, Renee Kazanis, Holly Rose Chinnery, Claude Charles Bernard, Paul McMenamin; Functional characterisation of CD11c-eYFP+ cells during systemic inflammation reveals that the mouse retina is devoid of antigen presenting cells. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5746.
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© ARVO (1962-2015); The Authors (2016-present)
The question of whether the CNS contains professional antigen presenting cells (APCs) has been debated for many years. We previously reported that putative dendritic cells in the neural retina of CD11c-eYFP Crb1wt/wt mice are phenotypically indistinguishable from microglia in the normal eye; however, their functional capacity has not been investigated. We hypothesised that retinal CD11c-eYFP+ cells are a subset of microglia and thus would have a limited capacity to present antigen to naïve T cells.
We first tested the ability of retinal CD11c-eYFP+ cells to upregulate APC markers following systemic inflammation. CD11c-eYFP Crb1wt/wt mice received an i.p injection of LPS (9mg/kg, n=23) or saline (n=18) and retinas were collected 24h later for confocal microscopy and flow cytometry. Myeloid cells from the uveal tract (known to contain APCs) of Cx3cr1-GFP mice were also included for comparison. For functional studies, retinal CD11c-eYFP+ cells and microglia (CD45lo YFP-) were isolated from CD11c-eYFP Crb1wt/wt mice (n=20) 24h post-LPS injection by FACS. CD11c-eYFP+ cells from spleen and meninges were included as controls. Isolated cells were co-cultured with naïve OT-II CD4+ T cells and ovalbumin for 72h. T cell proliferation was measured by flow cytometry.
Retinal CD11c-eYFP+ cells retracted their processes and displayed a stout morphology 24h post-LPS injection. Despite this, retinal CD11c-eYFP+ cells did not upregulate I-A/I-E, or the co-stimulatory molecules CD80 and CD86, and were phenotypically identical to CD45lo CD11b+ F4/80lo I-A.I-E- microglia. In contrast, Cx3cr1-GFP+ cells in the iris/ciliary body and choroid expressed I-A/I-E, CD86 and significantly upregulated CD80 following LPS challenge (p<0.05). Both retinal CD11c-eYFP+ cells and microglia from LPS treated mice failed to induce T cell proliferation in vitro (0.9±0.4% and 0.5±0.07% proliferation respectively), whereas splenic and dural CD11c-eYFP+ cells were potent APCs that induced T cell proliferation and upregulation of CD44 (p<0.05).
Retinal CD11c-eYFP+ cells do not upregulate APC markers following systemic inflammation and are incapable of presenting antigen to naïve CD4+ T cells in vitro. Moreover, retinal CD11c-eYFP+ cells are phenotypically and functionally identical to microglia. These data provide new evidence that the retina is devoid of APCs.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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