CD40LG and systemic lupus erythematosus: However, lymphoproliferation had already initiated as evidenced by higher levels of total IgG and IgM in the plasma of 6-week-old MRL/lpr mice than the controls (Fig. 1B) and accumulations of B cells and double-negative (DN) T in the spleen and MLN of lupus-prone mice (Fig. 1C).