Importance of Mast-Cell-Derived Eosinophil Chemotactic Factor A on Granuloma Formation in Murine <i>Schistosomiasis japonica</i>: Evaluation Using Mast-Cell-Deficient W/W<sup>v</sup> Mice

Abstract

The role of mast-cell-derived eosinophil chemotactic factor A (ECF-A) on eosinophil-rich periovular granuloma formation was examined by using mast-cell-deficient WBB6F1-W/WV mice infected with Schistosoma japonicum. The average size of granulomas formed around newly deposited eggs in the liver of W/WV mice was significantly smaller than that observed in control +/+ mice. The number of adult worms recovered or specific IgE titers were comparable between W/WV and +/+ mice. In contrast, immediate-type hypersensitivity response to specific antigen and dialyzable low-molecular weight ECF in the serum was detectable only in infected +/+ mice. When naive bone marrow eosinophils were incubated with the dialyzable fraction of infected +/+ mice sera, chemotactic reactivity of eosinophils to ECF derived from S. japonicum eggs was significantly enhanced, although that to synthetic ECF-A was depressed. Similar effects were observed when naive eosinophils were treated with synthetic ECF-A. The dialyzable fraction of infected W/WV mice sera had no such modulating effect on the chemotactic reactivity of eosinophils. These results suggest that an immediate-type hypersensitivity reaction is important in the formation of eosinophilic granulomas around S. japonicum eggs, mainly through the modulating effect of mast-cell-derived ECF-A on the chemotactic reactivity of eosinophils.