Ultraviolet radiation causes less immunosuppression in patients with polymorphic light eruption than in controls

Area of Science:

• Immunology
• Dermatology
• Photobiology

Background:

• Polymorphic light eruption (PLE) is a common photodermatosis.
• It is hypothesized that PLE involves impaired ultraviolet radiation (UVR)-induced immunosuppression.
• This impairment may lead to delayed-type hypersensitivity to photo-induced antigens.

Purpose of the Study:

• To investigate the susceptibility of PLE patients to UVR-induced immunosuppression.
• To compare the immune response to 2,4-dinitrochlorobenzene (DNCB) after UVR exposure in PLE patients and controls.
• To assess the immune response to diphenylcyclopropenone (DPCP) without UVR exposure in both groups.

Main Methods:

• Thirteen PLE patients and 11 controls were exposed to 1 minimum erythema dose (MED) of UVR.
• Sensitization with 2,4-dinitrochlorobenzene (DNCB) was performed on UVR-exposed skin, and with diphenylcyclopropenone (DPCP) on non-irradiated skin.
• Reactivity was measured by skin thickness increase after challenge doses of DNCB and DPCP.

Main Results:

• A strong correlation was observed between reactivity to DNCB and DPCP across all subjects.
• The reaction to DNCB relative to DPCP was significantly greater in PLE patients than in controls.
• This indicates that UVR suppressed DNCB sensitization less in PLE patients.

Conclusions:

• Patients with polymorphic light eruption exhibit a partial failure of UVR-induced immunosuppression.
• The induction of sensitization by 2,4-dinitrochlorobenzene is less suppressed by UVR in PLE patients compared to healthy individuals.
• This finding supports the hypothesis that impaired UVR-induced immunosuppression plays a role in the pathogenesis of PLE.