In addition to the elevated levels of sCD154 in circulation and the overexpression of CD154 in multiple immune cells, CD40 is also upregulated on the surface of B cells and macrophages of SLE patients as well as on the endothelial and mesangial cells of the kidneys in those with class III and IV LN [3,54]. Here, CD40LG is linked to systemic lupus erythematosus.