CGAS and systemic lupus erythematosus: Of relevance to human SLE, pre-treatment of mice with hydroxychloroquine (HCQ), a TLR and cGAS antagonist23 that has demonstrated efficacy in treating cutaneous lupus in patients with an IFN signature24, significantly decreased the early IFN-I scores in both the skin and the blood after exposure to UVB light (Fig. 2D).