Second, to determine the underlying mechanisms of increased B lymphopoiesis and ABC production in the skull BM of AD mice, we quantified immune factors from the skull BM and found that IL-6 level was greatly increased in 3-month-old 5×FAD mice (Fig. 4e) while that of other cytokines, such as IL-2, IL-4, IL-5, IL-10, TNF-α and IFN-γ, did not differ. Here, IL6 is linked to Alzheimer disease.