Constitutive expression of OX40L on T cells has been shown to induce spontaneous autoimmunity in C57BL/6 mice.23 A recent study showed that OX40L expression on a subset of myeloid DCs is implicated in the pathogenesis of SLE.28 The beneficial effect of blocking the OX40L-OX40 signalling pathway has been shown in several different mouse models of autoimmune diseases,17 but experimental evidence of its efficacy in SLE is unknown. The gene discussed is TNFSF4; the disease is systemic lupus erythematosus.