Ultraviolet (UV) Radiation Although UV radiation exposure may exacerbate pre-existing SLE, it remains unclear whether UV exposure plays a role in the pathogenesis of SLE(62). Experimental studies suggest that UV-B radiation results in induction of reactive oxygen species, leading to DNA damage(63), production of novel forms of autoantigens and autoreactive T cells(64, 65), and may have immunomodulatory effects on T cells and cytokines (66, 67), all potentially involved in to SLE pathogenesis. Only a few case-control studies have been able to examine UV radiation exposure and risk of SLE(68–70), and these have been limited by potential inaccuracy of exposure assessment, and influenced by recall and reverse causation bias, given that photosensitivity due to SLE can be present well before diagnosis. We have recently reviewed this topic in detail elsewhere(71). Large, well-controlled studies are still needed to prospectively assess the relationship of UV-B radiation with incident SLE.