Increased TGF‐β–producing CD4 + T lymphocytes in postburn patients and their potential interaction with dermal fibroblasts in hypertrophic scarring

The development of hypertrophic scar involves a complex interplay between cells and cytokines. Although the mechanism underlying its pathogenesis is not well understood, a polarized T‐helper type 2 immune response has been reported, indicating a role for CD4+ T lymphocytes in hypertrophic scarring. Here, we report an increased frequency of CD4+/transforming growth factor‐β (TGF‐β)‐producing T cells in the peripheral blood and hypertrophic scar tissue of burn patients. These cells may play an indirect regulatory role in hypertrophic scar by affecting the functions of dermal fibroblasts. Our results show an increase in cell proliferation and collagen synthesis by dermal fibroblasts treated with medium derived from burn patient CD4+ T lymphocytes but not from the CD4+ T cells of normal subjects. Using confocal microscopy and immunoblotting, we found the level of α‐smooth muscle actin to be elevated in these treated dermal fibroblasts, which also showed an enhanced ability to contract collagen lattices. TGF‐β levels in medium conditioned by the culture of CD4+ T lymphocytes from burn patients were significantly higher than in the conditioned medium from CD4+ T lymphocytes of normal subjects. In addition, the application of a TGF‐β–neutralizing antibody significantly reduced the effect of burn patient CD4+ T lymphocyte medium on dermal fibroblast proliferation and collagen lattice contraction. Our study suggests that CD4+/TGF‐β–producing T lymphocytes may play an important role in postburn hypertrophic scarring.