Fox-P3-positive regulatory T cells are present in the skin of generalized atopic eczema patients and are not particularly affected by medium-dose UVA1 therapy

Background: Regulatory T cells (T-reg cells) have been described as an important cell population in the UV treatment of inflammatory skin diseases. Methods: We have treated five patients with generalized atopic eczema (AE) using medium-dose (15 cycles of 50 J/cm², total dose of 750 J/cm²) UVA1 therapy and have analyzed the skin-infiltrating T-cellular subsets before and after therapy. Skin biopsies were split for immunohistochemistry and Real-time PCR and analyzed for CD4, Fox-P3, GATA-3, and IL-10 transcription as well as for CD3, CD4, CD152, Fox-P3, and GITR staining. Results: In all the investigated patients, we observed a good clinical response to UVA1. As described previously, the number of epidermal T cells slightly declined after irradiation. However, we did not observe a general decrease in T cell numbers. Within the population of T cells, no specific difference in the kinetics of Fox-P3-positive cells and Fox-P3-specific mRNA was noted as compared with GATA-3 positive T cells. These results were paralleled by RT-PCR for IL-10 and staining for CD152, a surface molecule that has been described for T-reg cells. Conclusion: In our hands, the clinical benefit of UVA1 treatment in AE patients does not seem to be due to a preferential survival/ proliferation of T-reg cells.