CD40LG and Autoimmunity: B cell CD154 expression has a precedent in human disease, as it is expressed by both T cells and B cells in systemic lupus erythematosus (SLE) patients and in a mouse model of lupus [16], [17], [18], with ectopic B cell expression of CD154 in aged hemizygous CD154TG mice leading to intestinal inflammation [19] or SLE-like autoimmunity including anti-DNA autoAbs and glomerulonephritis [20].