Distinct Plasmacytoid Dendritic Cell-T Cell Contacts in Draining Lymph Nodes Define T Cell Responses during Acute Herpes Simplex Virus Keratitis

Abstract

Purpose : Plasmacytoid dendritic cells (pDCs), are specialized immune cells residing in the cornea and play a key role in linking innate and adaptive immunity. In this study, we investigated the dynamic changes of pDCs-T cell interactions in draining lymph nodes (dLNs) that define the T responses in acute herpes simplex virus (HSV)-1 keratitis

Methods : Intravital multiphoton microscopy (IV-MPM) was performed in living mice to image dLNs in bone marrow chimera mice from Tred (T cells are red) x pDC-GFP (pDCs are green) mice during steady state and after corneal inoculation with TLR-9 agonist or HSV-1 to study the kinetics of pDC/T cell interactions. Number of contacts (N), short (<5min) and long contact time (>5min or >30min) were analyzed. Local pDCs were depleted by subconjunctival injections of diphtheria toxin or PBS (sham) in BDCA-2-DTR Tg mice. dLN were excised and assessed for T cell phenotype by flow cytometry with CD45 (pan-leukocytes marker), CD3 (T cells), CD8, and CD4, and production of IL-6 and TGF-β1

Results : IV-MPM imaging in dLNs showed pDC-T cells interactions after corneal inoculation of TLR-9 agonist compared to steady state with a high percentage having long contact time >5min (53.8% vs. 19.2%) and >30min (23.1% vs. 0%)(P<0.01). Interestingly, we identified dLNs areas with T cell clusters after HSV-1 keratitis, where pDCs interacted with high number of T cells (N=3.0) compared to steady state (N=1.5, p<0.01); and a high percentage having long contact time >5min (50.0%) and >30min (15.4%) compared to areas without T cell clusters (15.4% and 0%, respectively; P<0.01) or during steady state (20.0% and 0% respectively; P<0.01). dLNs from corneal pDC-depleted mice showed an increased density of CD4 and CD8 T cells (2.1-fold and 2.3-fold) compared to sham group (P<0.001), as well as increased IL-6 secreting T cells (3.4-fold) and reduced TGF-β1 secreting T cells (0.58-fold) during HSV-1 keratitis

Conclusions : Intravital imaging of dLNs demonstrates distinct pDCs-T cell interaction patterns, predominantly in areas with T cell clusters during acute HSV-1 keratitis. Moreover, pDC limit IL-6, but enhance TGF-β expression by T cells in concordance to the increase in Th17 over Tregs response previously observed by our group. Together, our data suggests that pDCs are involved in the T cell fate through direct interaction with T cells in HSV-1 keratitis

This is a 2021 ARVO Annual Meeting abstract.