In vitro analysis of immunoprotective effects of topical sunscreens

The aim of this study was to evaluate procedures for the assessment of the immunoprotective capacities of topical sunscreens, using cell cultures. The exposure of humans to solar or ultraviolet radiation has been shown to induce numerous changes at the level of the immunoresponsiveness of the skin, which could be described as immune suppression. In this study, a sunscreen containing the commercially available UVB filters octyl triazone, phenylbenzimidazole sulfonic acid and methylbenzylidene camphor, was tested because of its capacity to protect from the immunosuppressive effects of UVB radiation. In contrast to control suncreens with a comparable sun protector factor (SPF), but that did not contain the UVB-filter octyl triazone, the immunoprotective sunscreen protected from two forms of immune suppression as assessed in vitro. Expression of the immune-relevant cellular communication structure intercellular adhesion molecule-1 is decreased on the cell surface of epidermal cells under the influence of UVB. This effect of immune suppression is totally abolished by the immunoprotective capacity of the tested sunscreen, as monitored cytofluorometrically. The mixed-lymphocyte reaction (MLR) was also used to assess the protective capacities of sunscreens against UVB-radiation-induced suppression of the immune response. Again, this UVB-induced suppression of the MLR was prevented by the sunscreen containing octyl triazone. In summary, the results of this study demonstrate the usefulness of the above-mentioned methods for the in vitro evaluation of the immunoprotective properties of topical sunscreens.