Abstract
Purpose:
Plasmacytoid dendritic cells (pDCs) represent a highly functional subset of bone marrow (BM)-derived cells and play a key role in linking the innate and adaptive immune responses. The aim of this study is to investigate the role of corneal pDCs in adaptive immune responses after acute herpes simplex virus (HSV)-1 infection
Methods:
Corneal HSV infection was induced by inoculation of HSV-1 McKrae strain after scarification. Corneal pDCs were depleted by subconjunctival (s.c.) injection of diphtheria toxin (DT) or by PBS (sham controls) into BDCA-2-DTR mice 24h before virus infection and repeated every 2 days. Clinical corneal opacity was scored on a 0-4 scale. Submandibular draining lymph nodes (dLNs) were excised and quantified for IL-6 and TGF-β1 mRNA or assessed by flow cytometry for CD45 (pan-leukocyte marker), NK 1.1 (NK cells), CD11c (conventional dendritic cells [cDCs]), CD19 (B cells), CD3 (T cells), CD8, CD4, CD25 FoxP3 (Treg), IL-17 (Th17) and IFN-γ (Th1)
Results:
We observed a significant increase in corneal opacity in pDC-depleted corneas at days 3 (3) and 7 (3.4) as compared to sham controls (1.2 and 1.5 respectively, P<0.001) after HSV inoculation. Similarly, a significantly increased influx of total T cells (2.5-fold) and B cells (2.3-fold) on day 3, and 1.6-fold and 2.3-fold respectively on day 7 (P<0.05) was seen in dLNs of pDC-depleted corneas, as compared to sham controls. Further, dLNs from pDC-depleted corneas showed increased Th17 cells (1.6-fold and 2.1-fold) compared to sham and non-infected controls respectively, while a reduced frequency of Treg cells (0.74-fold) at day 3 as compared to both controls. In contrast, CD8+ T cells, Th1 cells, cDCs, and NK cells did not show significant changes in dLNs. Moreover, corneal pDC-depletion resulted in up-regulation of TGF-β1 (P<0.001) and IL-6 (P<0.05) mRNA at day 3 in dLNs compared to sham and non-infected controls. Similarly, corneal IFN-α depletion showed an increased Th17 cells (2.2 fold) at day 7 with a reduced Treg cells at day 5 (0.7-fold) in dLNs (P<0.01)
Conclusions:
Our data showed that corneal pDC-depletion results in increased frequency of total T cells and B cells, with shift in the balance of Treg cells toward Th17 cells in local dLNs and down-regulation of IL-6 and TGF-β1. Corneal pDCs may regulate the adaptive immune responses in dLNs through IFN-α in acute corneal HSV-1 infection