The Antigen-Presenting Activity of Fresh, Adult Parenchymal Microglia and Perivascular Cells from Retina

Abstract

Although several observations show local T cell recognition of retinal Ag, there has been no direct demonstration that the APC were retinal derived, rather than recruited. In this study, CD45+ cells isolated from immunologically quiescent murine retina were tested in vitro for functional evidence of Ag presentation to naive and Ag-experienced CD4 T cells specific for β-galactosidase. Because CD45+ cells from brain have been reported to be efficient APC, they were included for comparison. Measures of activation included changes in CD4, CD25, CD44, CD45RB, CD62L, CD69, caspase-3 activation, CFSE dilution, size, number of cells recovered, and cytokine production. Retinal CD45+ cells gave no evidence of Ag-dependent TCR ligation in naive T cells, unlike splenic APC and CD45+ cells from brain, which supported potent responses. Instead, addition of retinal CD45+ cells to cocultures of naive 3E9 T cells plus splenic APC reduced the yield of activated T cells and cytokine production by limiting T cell activation at early time points. Ag-experienced T cells responded weakly to Ag presented by retinal CD45+ cells. Activating the retinal cells with IFN-γ, anti-CD40, or LPS incrementally increased their APC activity. Addition of neutralizing Abs to TGF-β did not reveal suppressed retinal APC activity. Because retina lacks tissue equivalents of meninges and choroid plexus, rich sources of dendritic cells in brain, cells from retina may better represent the APC activity of fresh, adult CNS parenchymal and perivascular cells. The activity of the retinal CD45+ cells appears to be directed to limiting T cell responses.

Analysis of retinal cellular infiltrate in experimental autoimmune uveoretinitis reveals multiple regulatory cell populations

“…1B,C). In the eyes of unimmunized mice (6-12 weeks of age) we identified a population of CD11b þ cells (658 AE 54), drawn from the resident perivascular and parenchymal microglial cells [16,17] and a small number (24 AE 5) of CD4 þ cells (Table 1 and Fig. 1).…”

Lipopolysaccharide is a frequent and significant contaminant in microglia‐activating factors

“…For this purpose, microglia are equipped with an array of sensitive receptors, including TLRs for PAMPs such as LPS (Olson and Miller, 2004). LPS induces a broad spectrum of microglial activation parameters including NO/cytokine release (Kim et al, 2004), antigen presentation (Gregerson et al, 2004), and upregulation of surface antigens (Kloss et al, 2001;Menendez Iglesias et al, 1997;Terrazzino et al, 2002). LPS also modulates microglial proliferation, enhancing it in some experimental paradigms (Lee et al, 1994) and inhibiting it in others (Bianco et al, 2006;Ganter et al, 1992;GebickeHaerter et al, 1989;Northoff et al, 1989).…”

A look at autoimmunity and inflammation in the eye

“…Although there are resident dendritic cells in the retina that could serve as APCs, their expression of MHC class II molecules is low, at least until inflammation is underway (53). CD45 + cells derived from the circulation are sufficient to provide APC function, even without eye-resident APCs (54). It can be calculated by infusing labeled retina-antigen-specific T cells that fewer than ten such T cells must reach the eye to trigger the early changes leading to EAU (24).…”