title: Density and proportions of the epidermal T cell population in human sun-exposed skin differ from those in sun-protected skin: preliminary immunohistochemical study.
abstract: Epidermal T cells, which are found in clinically normal human skin, show topographic differences in density and proportions; however, the mechanisms and the biological consequences of such differences are still unknown. In a previous work, we showed that epidermal T cells are altered in number and composition after a single exposure to solar-simulated radiation (SSR). The purposes of the present investigation were, first, to compare the density of epidermal T cells and the proportion of T cell subpopulations in habitually sun-exposed versus sun-protected sites; second, to determine the effects of repetitive exposures to SSR on the latter cell populations. Biopsies from habitually sun-exposed, sun-protected and solar-simulated-exposed skin of 28 healthy volunteers were taken and immunohistochemistry was performed on cryostat sections. Compared with sun-protected sites, epidermal CD3(+) T cell numbers of habitually sun-exposed sites were significantly lower. Double staining showed that the number of CD3(+)CD8(+) T cells was significantly lower in sun-exposed than in sun-protected skin, whereas the numbers of CD3(+)CD4(+) T cells were similar in both sites. Therefore, the CD4/CD8 ratio was markedly higher in sun-exposed compared to sun-protected sites. Moreover, repeated exposures of sun-protected skin to SSR induced a significant reduction in number of epidermal CD3(+) T cells. The mean number of epidermal CD3(+)CD8(+) double stained cells significantly decreased after such exposures, while the epidermal CD3(+)CD4(+) T cell subpopulation was not significantly changed. In conclusion, both chronically sun-exposed skin and repeatedly SSR-exposed skin show a decrease in density of epidermal CD3(+) and CD3(+)CD8(+) T cells. We hypothesize that such sun-induced changes may weaken the immunosurveillance capacity of the skin and therefore increase the occurrence of skin cancer.
authors.affiliation: Section of Dermatology, Department of Surgery, University of Parma, Via Gramsci 14, Parma, Italy. sergio.dinuzzo@unipr.it
authors.forename: Sergio
authors.initials: S
authors.lastname: Di Nuzzo
authors.forename: Pierpaolo
authors.initials: P
authors.lastname: Pavanello
authors.forename: Giuseppe
authors.initials: G
authors.lastname: De Panfilis
mesh_terms: D000328:Adult; D001706:Biopsy; D017252:CD3 Complex / Q000378:metabolism*; D016516:CD4-CD8 Ratio; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology* / Q000276:immunology / Q000528:radiation effects; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology*; D002452:Cell Count; D004307:Dose-Response Relationship, Radiation; D000078404:Epidermal Cells; D004817:Epidermis / Q000528:radiation effects*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012867:Skin / Q000473:pathology; D013472:Sunlight; D013601:T-Lymphocytes / Q000166:cytology* / Q000276:immunology / Q000528:radiation effects; D050378:T-Lymphocytes, Regulatory / Q000166:cytology / Q000276:immunology / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D017252:CD3 Complex