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Arsia Jamali, Maria J. Lopez, Deshea L Harris, Pedram Hamrah; Corneal plasmaytoid dendritic cells subpopulations demonstrate differential expression of the functional Siglec-H receptor that are altered after corneal inflammation. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3215.
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Plasmacytoid dendritic cells (pDCs), a subset of immune cells, are recognized as powerful orchestrators of innate and adaptive immunity. Siglec-H, a specific pDC marker, modulates interferon-α production. While Siglec-Hlow pDCs are the main source of interferon-α in some tissues, the specific role of pDC subpopulations remains unclear. We have previously demonstrated presence of resident corneal pDCs in steady state. This study aims to characterize the presence and distribution of corneal pDC subpopulations in steady-state and inflammation.
Corneal inflammation was induced by intrastromal suturing or thermal cautery in adult C57BL/6 mice and compared to naïve controls. 3 days after cautery and 14 days after suturing, corneas were stained for CD45 (pan-leukocyte marker), Siglec-H (functional pDC marker), and PDCA-1 (pDC marker) and underwent confocal microscopy. Flow cytometry of corneal single cell suspension was performed on day 7 after suturing via CD45, Siglec-H, PDCA-1, CD40, and MHC-II antibodies. T-test and ANOVA were used to assess statistical significance.
PDCA-1+ cells were observed in the periphery (82.2±5.1 cells/mm2) and center (51.6±4.9) of naïve corneas. In the periphery, 43.5% of PDCA-1+ cells were Siglec-H+; sub-grouped to Siglec-Hhigh (33.1%) and Siglec-Hlow (11.1%) pDCs. In the center, these figures were 23.4%, 9.7%, and 17.7%, respectively. On day 14 after suturing, the density of corneal PDCA-1+ cells in the periphery (208.0±23.8) and center (132.4±19.1) significantly increased (p<0.003). Further, Siglec-Hlow pDCs increased 7 fold in the periphery and 5 fold in the center (p<0.001). Flow cytometry confirmed the increase of pDCs in inflammation and showed that 98.9±1.9% of CD45+PDCA-1+Siglec-Hhigh cells co-expressed MHC-II while 65.5±7.7% of CD45+PDCA-1+Siglec-Hlow and 20.7±6.4% of CD45+PDCA-1+Siglec-H- cells expressed MHC-II (p<0.001). For co-expression of CD40, these numbers were 98.1±1.7%, 32.2.5±1.5%, and 1.6±0.7%, respectively (p<0.001).
Our findings demonstrate the presence of Siglec-H+ pDCs in the cornea, with differential expression of Siglec-H and increased activation markers in Siglec-H+ pDCs. During inflammation, there is a shift towards increased Siglec-Hlow pDC subpopulation. Further studies are underway to assess the functional role of these populations.
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