Plasmodium berghei infection ameliorates atopic dermatitis-like skin lesions in NC/Nga mice

BACKGROUND Atopic diseases are more prevalent in industrialized countries than in developing countries. In addition, significant differences in the prevalence of allergic diseases are observed between rural and urban areas within the same country. This difference in prevalence has been attributed to what is called the 'hygiene hypothesis'. Although parasitic infections are known to protect against allergic reactions, the mechanism is still unknown. The aim of this study was to investigate whether or not malarial infections can inhibit atopic dermatitis (AD)-like skin lesions in a mouse model of AD. METHODS We used NC/Nga mice which are a model for AD. The NC/Nga mice were intraperitoneally infected with 1 × 10(5) Plasmoduim berghei (Pb) XAT-infected erythrocytes. RESULTS Malarial infections ameliorated AD-like skin lesions in the NC/Nga mice. This improvement was blocked by the administration of anti-asialo GM1 antibodies, which are anti-natural killer (NK) cells. Additionally, adoptive transfer of NK cells markedly improved AD-like skin lesions in conventional NC/Nga mice; these suggest that the novel protective mechanism associated with malaria parasitic infections is at least, in part, dependent on NK cells. CONCLUSIONS We have experimentally demonstrated for the first time that malarial infections ameliorated AD-like skin lesions in a mouse model of AD. Our study could explain in part the mechanism of the 'hygiene hypothesis', which states that parasitic infections can inhibit the development of allergic diseases.