For example, mice deficient in secreted IgM (sIgM-/-) show increased susceptibility to acute peritonitis in a cecal ligation puncture model (Jenck et al., 1998), but also a stronger tendency of developing an auto-immune phenotype upon LPS injection or when crossed onto the lupus prone lpr background (Boes et al., 2000). Here, CD40LG is linked to systemic lupus erythematosus.