A previous study reported an improvement in SLE after treatment with monoclonal antibodies against OX40L, with a decrease in the levels of IFN-gamma, IL-6 and anti-dsDNA antibody, which supports a role for OX40L in SLE pathogenesis.13 OX40L has been reported to be abundantly present in glomeruli in renal biopsies of almost all cases of proliferative LN, which supports a role for OX40L in LN.16 On the other hand, Patschan et al14 did not find any significant difference in serum-soluble OX40L concentration between SLE patients and healthy controls. Here, TNFSF4 is linked to systemic lupus erythematosus.