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. This evidence concerns the gene TNFSF4 and autoimmune disease.