Bone marrow-derived cells in mouse and human cornea

Recently published experimental data on the distribution of bone marrow (BM)-derived cells in human and mouse corneas in comparison with in human skin/oral mucosa are reviewed. In mouse corneal epithelium, major histocornpatibility complex (MHC) class II-negative dendritic cells (DC) are present. Immature MHC class II-negative and mature MHC class II-positive DC are present in the center and periphery of the anterior corneal stroma, respectively. Monocyte (Mo)/macrophage (M Phi) lineage cells including the M Phi marker F4/80-expressing cells reside in the posterior stroma. In human cornea, MHC class II (HLA-DR)-positive miniature myeloid DC (CD11c(+) CD16(-), CD11c(+)CD16+, and CD11c(+)CD1c(+)) and Mo/M Phi lineage cells are detectable in the corneal epithelium and stroma, respectively. Distribution of Mo/M Phi lineage cells (HLA.DR(+)CD11b(+)CD11c(+)CD14(+)) is predominant in the anterior stroma of the central cornea and all layers of the peripheral cornea. Both the phenotypes and distribution pattern of these cells in human cornea are different from those of human skin and nasal rnucosa. These findings suggest that BM-derived cells in normal human cornea are present in situ in preparation for foreign antigen and pathogens and have critical roles in innate and acquired immunity of the ocular surface.