T Lymphocytes Attenuate Dermal Scarring by Regulating Inflammation, Neovascularization, and Extracellular Matrix Remodeling

Objective: While tissue injury and repair are known to involve adaptive immunity, the profile of lymphocytes involved and their contribution to dermal scarring remain unclear. We hypothesized that restoration of T cell deficiency attenuates dermal scarring. Approach: We assessed the temporal-spatial distribution of T lymphocytes and their subtypes during the physiological dermal wound repair process in mice. Also, we compared the scarring outcomes between wild-type (WT) and severe combined immunodeficient (SCID) mice, which are lymphocyte deficient. Complementary gain-of-function experiments were performed by adoptively transferring lymphocyte subsets to validate their contribution to tissue repair in wounded SCID mice. Results: CD4⁺ T lymphocytes were present within dermal wounds of WT mice beginning on day 1 and remained through day 30. Wounds of SCID mice exhibited accelerated closure, increased inflammation, limited neovascularization, and exacerbated scarring compared with WT mice. Conversely, transfer of either mixed B and T lymphocytes or CD4⁺ lymphocytes alone into SCID mice resulted in moderated healing with less inflammation, collagen deposition, and scarring than control SCID wounds. In contrast, transfer of other lymphocyte subsets, including helper T lymphocytes (CD3⁺CD4⁺CD25^-), CD8⁺ T cells and B cells, or regulatory T lymphocytes (CD4⁺CD25⁺CD127^low), did not reduce scar. Innovation: The finding that lymphocytes delay wound healing but reduce scar is novel and provides new insights into how dermal scarring is regulated. Conclusion: Our data support a suppressive role for CD4⁺ T cells against inflammation and collagen deposition, with protective effects in early-stage dermal wound healing. These data implicate adaptive immunity in the regulation of scarring phenotypes.