Regulatory T cell mediated suppression of dendritic cells in a mouse model of dry eye

Abstract

Purpose: To evaluate the immunosuppressive properties of regulatory T cells, Tregs, against dendritic cell activation following induction of experimental dry eye disease.

Methods: C57Bl/6 wild-type female mice were exposed to desiccating environmental stress (DS; low humidity <40%, constant airflow, and subcutaneous scopolamine dosing) for up to 10 days. Flow cytometry was used to characterize CD4+ Tregs within the cervical lymph nodes and spleen to i.) distinguish the frequencies of inducible and natural regulatory T cells (iTregs and nTregs, respectively) using Helios or Neuropilin-1 as putative markers for thymus-derived nTregs, ii.) evaluate Treg immune suppression of dendritic cell maturation by cell-contact mediated by CTLA4 and LAG3, and by paracrine signaling mediated by IL-10 and TGF-β (LAP) inhibitory cytokines.

Results: The frequencies of CD4+ iTregs and nTregs were significantly increased at day 3 DS (p≤ 0.01), while these populations decreased at day 10 DS, relative to controls. CD4+ iTregs and nTregs showed significantly increased expression of CTLA4 and LAG3 (p<0.001), and increased IL-10 and TGF-β expression at day 3 DS, compared to controls. Co-culture of bone-marrow derived dendritic cells with DS-derived Tregs resulted in a greater dose-dependent decrease in dendritic cell maturation compared to control-derived Tregs. Furthermore, suppression of dendritic cells by Tregs derived from control mice was contact-dependent, while paracrine-mediated inhibition contributed to DS-derived Treg suppression.

Conclusions: These results indicate that iTregs and nTregs increase early in response to desiccating stress and have an increased ability to suppress dendritic cell maturation by paracrine-mediated inhibition.

Keywords: 555 immunomodulation/immunoregulation • 486 cornea: tears/tear film/dry eye • 557 inflammation