Elucidation of mechanism of the protection against allergies by LPS

We examined mechanisms for the prevention of allergic reactions by infections from the point of view of the relation between LPS (lipopolysaccharide)-priming and antigen-uptake capacity of dendritic cells. First, we established an experimental model, in which LPS, as an endotoxin, protected mice against the subsequent development of allergic reactions. The accumulation of antigen up-taking cells in the lymph nodes in LPS-primed mice was significantly less than that in control mice. Interestingly, the age and term of LPS-priming were important for the prevention of lymph node-homing antigen. In addition, the uptake of antigen in bone marrow derived-dendritic cells (BMDCs) was lowered in LPS-primed mice than in control mice. The LPS-priming induced the expression of the inducible nitric oxide synthase (iNOS) and the highly NO-production in BMDCs. Furthermore, the iNOS inhibitor recovered the capacity of antigen-uptake in BMDCs from LPS-primed mice.