Eicosanoids mediate induction of immune genes in the fat body of the silkworm, Bombyx mori

The expression of cecropin and lysozyme genes is induced in response to bacterial peptidoglycan in the fat body of the silkworm, Bombyx mori. Specific inhibitors of either phospholipase A 2, cyclooxygenase or lipoxygenase significantly inhibit the induction of the immune genes both in vivo and in cultured fat body as detected by means of Northern hybridization. Arachidonic acid injected into the larvae induces the expression of the cecropin and lysozyme genes. The findings support the idea that eicosanoids mediate some process leading to the expression of immune genes in the fat body following recognition of peptidoglycan as a signal for invading bacteria.