Induction of protective immunity by primed B-1 cells in Toxoplasma gondii -infected B cell-deficient mice

We examined the role of B‐1 cells in protection against Toxoplasma gondii infection using B cell‐deficient mice (μMT mice). We found that primed but not naïve B‐1 cells from wild‐type C57BL/6 mice protected B cell‐deficient recipients from challenge infection. All μMT mice transferred with primed B‐1 cells survived more than 5 months after T. gondii infection, whereas 100% of μMT mice transferred with naïve B‐1 cells succumbed by 18 days after infection. Additionally, high expression of both T help (Th) 1‐ and Th2‐type cytokines and a high level of nitric oxide production were observed in T. gondii‐infected μMT mice transferred with primed B‐1 cells. Thus, it was clearly demonstrated that B‐1 cells play an important role in host protection against T. gondii infection in μMT mice.