Summary of the Leiden work for SUNALL website

The clinic in Leiden participates in the questionnaire studies on PLE patients and people from the general population. Next to that, the Leiden group focusses on the effects of various UV irradiation sources on epidermal and dermal cell infiltrates, and on cytokine shifts in PLE patients in comparison to photosensitive lupus erythematosus (LE) patients and in healthy individuals.
The basic hypothesis is that UV irradiation causes an imbalance in immune responses in patients with PLE. UVB-induced immune suppression is decreased in these patients and therefore UV exposure will eventually lead to a cascade that results in a delayed type hypersensitivity reaction to putative UV modified skin components. One of the interesting findings that strengthen this hypothesis is the observation of Kolgen et al. that epidermal Langerhans cells (LC) persist in the epidermis upon UVB overexposure in PLE patients. This phenomenon was also observed in one patient with photosensitive LE, who was mistakenly included in this study. In clinical practice LE can be an important differential diagnosis of PLE. We have therefore decided to expand this experiment to a larger group of patients with several forms of cutaneous and photosensitive LE to investigate whether they share a common pathogenic mechanism with PLE, reflected in a hampered migration of LC. In another experiment, we have subjected several PLE patients to UVB hardening therapy, and we will investigate the effect of UV hardening on epidermal Langerhans cells, macrophages and neutrophils before and after therapy. The UVB adaptation will also be investigated in healthy individuals, and we aim to investigate shifts in cytokines harvested from suction blisters before and after UV treatment. Because UVA is often found to be especially effective in provoking PLE, and UVA has recently been reported to induce cytokines quite different from UVB, we will also investigate UVA-induced cytokine profiles.