ROLE OF THE INTEGUMENT IN INSECT IMMUNITY - EPICUTICULAR ABRASION ANDINDUCTION OF CECROPIN SYNTHESIS IN CUTICULAR EPITHELIAL-CELLS

When the epicuticle of a silkworm larva, Bombyx mori, was lightly abra ded in the presence of live Bacillus licheniformis, Enterobacter cloac ae, or bacterial cell wall components, cecropin mRNAs were detected in the underlying epithelial cells and in fat body cells remote from the abraded area. Antibacterial activity due to cecropin was detected in the matrix of the lightly abraded cuticle but not in nonabraded portio ns of the cuticular matrix or in the hemolymph surrounding the fat bod y, unless a more severe cuticular abrasion was administered. A light a brasion to a larva of the giant silkworm moth, Hyalophora cecropia, in the presence of E. cloacae also induced antibacterial activity in the abraded cuticle. These data illustrate that the ectodermally derived lepidopteran larval integument, when challenged by live bacteria or th eir cell wall components, mounts an immune response. Hence, the insect exoskeleton, which is often considered as an inert protective armor, is indeed actively participating in defense.