The role of lymphocytes in human dermal wound healing

Background Animal experimental data indicate a requirement for functionally active T lymphocytes to allow optimal healing of dermal wounds. Little evi dence exists to confirm that this is the case in humans. Lymphocyte involve ment in regulation of healing is probably mediated by release of secreted c ytokines/growth factors, and we hypothesize that the cytokine profile requi rement will be modulated as healing progresses. Objectives As this is likely to be reflected in lymphocyte subset changes o ver the course of normal healing, we investigated the immunophenotype of ly mphocyte subpopulations during wound healing. Methods Sequential biopsies were taken over 42 days from the margin of 12 w ounds healing by secondary intention after pilonidal sinus excision. Serial biopsy sections were analysed by immunohistochemistry using lymphocyte-spe cific monoclonal antibodies, and lymphocytes were counted microscopically. Results Within 42 days, the mean decrease in wound volume was 87.5%. This w as accompanied by significant changes in the wound margin lymphocyte popula tion. Total numbers (mean +/- SEM) of T lymphocytes decreased from 36.8 +/- 9.8 cells per field at inclusion in the study to 25.9 +/- 3.0 immediately prior to wound closure, with a concomitant increase in B lymphocytes from 1 +/- 0.4 to 9.5 +/- 3.6 cells per field. The CD4/CD8 T-lymphocyte ratio fel l from an initial level of 3.6 +/- 0.3 to 2.1 +/- 0.3 (mean +/- SEM) prior to closure. Conclusions These data indicate that human wound-associated lymphocyte popu lations are modulated during healing; the increase in numbers of CD8+ T-sup pressor lymphocytes is in accordance with previous animal data, indicating a role for these cells in downregulating healing as the wound closes. This study also documents an associated increase in B lymphocytes and healing of human wounds, with an as yet undefined role.