CD4+ and CD8+ T Cells in Murine Wound Healing Models

The immune response induced by injury involves multiple types of inflammatory cells, including T cells. T cells play an important role in the cell-mediated immune response; however, their involvement in wound healing is not well understood. Hypothesis: Levels of CD4 and CD8 T cells increase through the time course of wound healing along with levels of the inflammatory cytokines released by these cells. Objectives: This project was designed to quantify CD4 and CD8 T cells in wounds, and to assess TNF-α and TGF-β1 gene expression in these populations. Methods: Following an ACC-approved protocol, 3mm excisional wounds were placed on BALB/c mice and harvested over the course of 22 days. CD4 and CD8 T cells were quantified using indirect immunofluorescence. T cells were isolated, and RT real time PCR was used to determine cytokine gene expression. Results: In wounds, CD4 cells increased sharply at day 3, peaked at day 5, and remained in significantly high numbers until day 10. CD8 cells displayed a gradual increase, peaked at day 7, and returned to the baseline levels by day 22.  Overall, there were more CD4 cells than CD8 cells in the wound bed. CD4 cells from day 5 wounds showed an increased expression of TNF-α and TGF-β1 when compared to the baseline splenic cells; CD8 cells did not show such increase. Conclusion: CD4 and CD8 T cells are present in the wound bed over the four stages of wound healing, with peak levels in both the late stage of wound inflammation and the early stage of proliferation and remodeling. CD4 cells collected from day 5 wound tissue express mRNA for TNF-α and TGF-β1.  Further studies are needed to understand how T cells and their released cytokines influence tissue remodeling and fibroblast function.