Immunolocalization of FXIIIa+ Dendritic Cells in Human Burn Wounds

Abstract

Dermal dendrocytes constitute a population of indigenous antisen-presenting cells that have been implicated in dermal inflammation and may have a role in wound healing. They are identified by expression of the transglutaminase coagulation Factor XIIIa (FXIIIa) and a perivascular distribution in the papillary dermis. In this study, we used immunohistochemistry to localize and characterize FXIIIa+ cells in healing burn wounds. Wound specimens from Postburn Days 2, 3, 4, 5, 6, 8, 9, 10, 11, 15, 30, and 49 were collected from 18 patients at the time of excision and grafting, processed for immunolabeling, and labeled with an antibody to FXIIIa. Tissue sections were also double-labeled with the anti-FXIIIa and with antibodies to CD68, specific for macrophases, CD45, specific for bone marrow-derived cells, and proliferating cell nuclear antigen (PCNA) for proliferation. Antigen-presenting status was evaluated using an antibody to the major histocompatibility complex HLA-DR. The dermis subjacent to the tongue of proliferating epithelium at the wound edge had increased numbers of FXIIIa+ dendritic cells compared to the cellular distribution in uninjured skin, FXIIIa+ dendritic cells were absent from the burned dermis on all postburn days examined in this study. However, capillaries in the deep dermis had a FXIIIa+ granular staining pattern. CD68+ cells and CD45+ cells were present throughout the wound bed at all stages of healing, indicating an inflammatory cell response in the injured dermis. Antibodies to PCNA did not colocalize to FXIIIa+ cells, suggesting that the dermal dendrocytes were not proliferating. The antibody to HLA-DR localized to some, but not all of the FXIIIa+ dendritic cells. We have identified FXIIIa+ dendritic cells at the edges of human burn wounds and have speculated that expression of FXIIIa may not represent a unique inflammatory cell type. Inconsistent localization of other inflammatory cell markers suggests that multiple cell types may express FXIIIa. If this is true, cellular expression of this common transglutaminase may relate to a state of cellular differentiation or activity. Further studies are needed to clarify the significance of FXIIIa expression by dermal cells in a wound bed.