Resident Innate Immune Cells in the Cornea.

Jun Liu,Zhijie Li

doi:10.3389/fimmu.2021.620284

Abstract

The cornea is a special interface between the internal ocular tissue and the external environment that provides a powerful chemical, physical, and biological barrier against the invasion of harmful substances and pathogenic microbes. This protective effect is determined by the unique anatomical structure and cellular composition of the cornea, especially its locally resident innate immune cells, such as Langerhans cells (LCs), mast cells (MCs), macrophages, γδ T lymphocytes, and innate lymphoid cells. Recent studies have demonstrated the importance of these immune cells in terms of producing different cytokines and other growth factors in corneal homeostasis and its pathologic conditions. This review paper briefly describes the latest information on these resident immune cells by specifically analyzing research from our laboratory.

Highlights

Barrier surfaces, such as the skin and mucosal membranes, are major interfaces with the outside environment and play critical roles in immune surveillance [1, 2]
At the earlier stage of embryonic development, mast cells (MCs) precursors are found in the fetal liver at E11. Consistent with this observation, we found that MCs exist in the presumptive cornea at E12.5 (Figure 2A) [67], which is the time of definitive hematopoiesis in the fetal liver—not the bone marrow [68]
Through whole-mount immunostaining of the cornea and flow cytometric analysis, we identified the composition and distribution of macrophages in mice using the highly specific macrophage marker, CD64 [85], in the cornea (Figure 3A) and categorized these cells into C-C chemokine receptor (CCR) type 2− and CCR2+ populations

Summary

Introduction

Barrier surfaces, such as the skin and mucosal membranes, are major interfaces with the outside environment and play critical roles in immune surveillance [1, 2]. The cornea is home to several immune cell populations that reside in both the central and peripheral corneal regions. These heterogeneous immune cell populations form a complex immune network that mainly comprises tissue-resident macrophages, Langerhans cells (LCs), MCs, lymphocytes, and ILCs. These immune cell subsets enable the cornea to respond to many environmental challenges by performing specialized functions [9].

Results

Conclusion