Nature Cell Biology 4, pp 26 - 31

Sunburn is painful, but that's actually the best possible response to too much exposure to sunlight. Indeed, ultraviolet (UV) radiation causes DNA damage in skin cells, and unless substantially damaged cells are eliminated by apoptotic cell death, these damaged cells might grow cancerous. But wouldn't it be better to repair the cell's DNA than to destroy the cell? That's what Thomas Schwarz and his colleagues have now achieved, as described in the January issue of Nature Cell Biology. They show that the cytokine interleukin-12 (IL-12) (a growth factor that regulates the function of the immune system) can boost the capacity of skin cells to repair DNA damage. Skin cells of mice exposed to UVB contain aberrant DNA structures called cyclobutane pyrimidine dimers (CPD). But when the mice were given IL-12 before exposure to UVB, no CPD could be detected. The extent of skin cell death was also significantly reduced in the presence of IL-12. Skin cells can thus be repaired and survive healthily. The authors also show that IL-12 works by increasing the expression of components of the DNA repair machinery.

So a little bit of IL-12 could enhance the protective effects of sun creams.