Normalized ultraviolet (UV) induction of Langerhans cell depletion and neutrophil infiltrates after artificial UVB hardening of patients with polymorphic light eruption

BACKGROUND

Ultraviolet (UV) B hardening has been widely used as a prophylactic treatment in patients with polymorphic light eruption (PLE). Recent investigations have shown that in patients with PLE Langerhans cells (LCs) and neutrophils display less migration from and to the epidermis after an intense UVB irradiation compared with controls.

OBJECTIVES

To investigate the effect of UVB hardening of patients with PLE on their cell migratory responses after intense UVB exposure.

METHODS

Thirteen patients with PLE were recruited and UVB provocation testing was performed before entering the study. Among these patients, seven developed PLE rash upon UVB provocation ('UVB-P') and the other six did not respond ('UVB-NP'). Eleven age/sex-matched controls were included. Buttock skin of all included individuals was exposed to 6 minimal erythema doses (MED) of UVB (TL-12 lamps). Biopsies were taken after 24 h and 48 h, together with one control biopsy of unirradiated skin. Patients received total-body UVB hardening therapy consisting of 12 irradiations, on average rising from 10% to 140% of the initial MED in 6 weeks. Subsequently, MEDs were reassessed and biopsies were taken from newly irradiated (6 MED UVB) and unirradiated buttock skin. Skin sections were stained for the presence of LCs, macrophages and neutrophils. The cross-sectional area (in percentage) of positively stained cells within the epidermis was assessed from patients before and after hardening and compared with controls.

RESULTS

Before therapy, epidermal LC depletion and neutrophil influx at 48 h after 6 MED were most significantly reduced in 'UVB-P' patients (P = 0.025 and P =0.006, respectively) when compared with controls. 'UVB-NP' patients did not differ significantly from controls. After therapy, there were no longer any significant differences in the cell numbers among these three groups.

CONCLUSIONS

UVB hardening significantly improves UV-induced cell migratory responses in patients with PLE. UVB provokability of PLE appears to be most strongly linked to reduced UVB-induced trafficking of LCs and neutrophils, and 'UVB-P' patients show normalization of these responses after UVB hardening.