Thus, in the future, C3d(g) dimers could have implications for the development of novel therapies for autoimmune diseases, for example through their effects on CD40/CD40L interactions, particularly as downregulation of CD40 was shown to be a beneficial outcome of Rituximab treatment of systemic lupus erythematosus (SLE) patients (60) and CD40/CD40L levels have been linked to anti-DNA autoantibody titres in lupus patients (61) and mouse models (62). Here, CD40LG is linked to systemic lupus erythematosus.