Decreased neutrophil skin infiltration after UVB exposure in patients with polymorphous light eruption

UV radiation, in particular UVB, suppresses the skin immune response. In patients with polymorphous light eruption (PLE) the skin immune response seems activated after UV exposure. Typical PLE skin lesions can occur as early as several hours after UV exposure. In healthy volunteers, neutrophils infiltrate the skin shortly after UV exposure. The kinetics and mechanisms of neutrophil infiltration in the skin of PLE patients after UVB exposure was studied. Skin biopsies at 0, 3, 6, and 18 h were taken from five PLE patients and six healthy controls after irradiation with three minimal erythema dose UVB. Furthermore, neutrophils were isolated from blood of five PLE patients and six healthy controls to test their chemotactic activity. Immunohistochemical analysis showed a significant decreased neutrophil infiltration in PLE skin after UVB irradiation compared with healthy controls (p<0.05). In both healthy controls and PLE patients, after UVB irradiation, ICAM-1 and E-selectin expression on endothelial cells increased at 6 h after irradiation. Blood neutrophil chemotactic response towards IL-8 and C5a, as well as the expression of cell surface markers involved in adhesion and chemotaxis, was not different between PLE patients and healthy controls. In conclusion, PLE is marked by a decreased skin infiltration of neutrophils after UVB irradiation, possibly leading to a diminished neutrophil-induced suppression.