The discovery of new receptors (αIIbβ3, α5β1, and αMβ2) for CD154 has expanded our understanding about the precise role of this critical immune mediator in the physiopathology of chronic inflammatory autoimmune diseases in general, and in systemic lupus erythematosus and rheumatoid arthritis in particular. This evidence concerns the gene CD40LG and systemic lupus erythematosus.